>>> TONIGHT, BREAKING NEWS ON PRESIDENT BIDEN'S HEALTH. THE PRESIDENT DIAGNOSED WITH COVID JUST BEFORE ADDRESSING A MAJOR LATINO VOTER EVENT IN A KEY SWING STATE. IT COMES AMID LINGERING QUESTIONS ABOUT HIS HEALTH AND WHAT HE SAID ABOUT HIS PLANS TO KEEP RUNNING. THE NEWS COMES FOLLOWING A NEW HIGH-PROFILE CALL FOR HIM TO EXIT THE RACE. >>> JD VANCE'S FIRST REPUBLICAN NATIONAL CONVENTION IS AS ITS VICE PRESIDENTIAL NOMINEE. HIS SELECTION SIGNALING THE POSSIBLE FUTURE OF THE PARTY. OUR LOOK INTO HIS RAPID RISE TO FORMER PRESIDENT TRUMP'S RUNNING MATE, THE SHARP CONTRAST VICE PRESIDENT HARRIS IS ALREADY DRAWING. >>> PLUS, THE NEW TIME LINE OF WHEN THE SECRET SERVICE SPOTTED THE WOULD-BE ASSASSIN AT THIS WEEKEND'S RALLY. AND MORE NEW DETAILS. HIS VISIT TO THE SITE DAYS BEFORE AND IMAGES TONIGHT SHOWING THE TRANSMITTER FOUND NEXT TO THE SHOOTER'S BODY. WHAT IT WAS DESIGNED TO DO. >>> AND JUST IN, SENATOR BOB MENENDEZ INTENDS TO RESIGN AFTER BEING FOUND GUILTY ON ALL COUNTS. >>> FLASH FLOOD EMERGENCY. HOMES AND BUSINESSES AND BRIDGES WASHED AWAY IN THE OZARKS AND THE SUDDEN DEADLY DELUGE IN THE NORTHEAST. >>> MYSTERY ABROAD, TWO AMERICANS DEAD AFTER A POSSIBLE POISONING IN A LUXURY HOTEL IN THAILAND. WHAT WE'RE FINDING. PLUS, THE CHILLING IMAGE OF THE CRIME SCENE. >>> SPEAKING OUT, NFL LEGEND TERRELL DAVIS SAYING HE WAS ARRESTED AND HUMILIATED ABOARD A UNITED FLIGHT IN FRONT OF HIS CHILDREN AFTER ASKING FOR A CUP OF ICE. >> Announcer: THIS IS "NBC NIGHTLY NEWS" REPORTING TONIGHT FROM THE REPUBLICAN NATIONAL CONVENTION IN MILWAUKEE. HERE IS LESTER HOLT. >>> AND GOOD EVENING FROM MILWAUKEE. WE BEGIN WITH THE BREAKING NEWS THAT PRESIDENT BIDEN HAS TESTED POSITIVE FOR COVID AFTER EXPERIENCING SYMPTOMS TODAY. THE NEWS COMING IN AFTER MR. BIDEN SPENT MUCH OF THE DAY CAMPAIGNING IN LAS VEGAS. HE WAS SEEN MOMENTS AGO BOARDING AIR FORCE ONE NOT DONNING A MASK. HE WAS SET TO BEGIN AN EVENT SPEAKING TO LATINO VOTERS THERE. THE PRESIDENT ALSO FACING A NEW CALL TO DROP OUT OF THE RACE FROM A KEY HOUSE DEMOCRAT. SENIOR WHITE HOUSE CORRESPONDENT KELLY O'DONNELL IS FOLLOWING IT ALL, AND, KELLY, I MUST NOTE THIS COMES JUST TWO DAYS AFTER I SAT DOWN TO INTERVIEW THE PRESIDENT AT THE WHITE HOUSE. HE APPEARED OKAY AT THAT TIME. WHAT MORE ARE YOU FINDING OUT ABOUT THE PRESIDENT'S CONDITION? >> Reporter: WELL, THIS WAS A SURPRISE, LESTER, AND IT MEANS THAT HE HAD TO SKIP A BIG CAMPAIGN SPEECH IN NEVADA. AS HE WAS GETTING ON THE PLANE, HE TOLD REPORTERS HE FEELS GOOD. HE WILL GO TO HIS HOME IN REHOBOTH BEACH, DELAWARE, AND OFFICIALS I TALKED TO SAID HE WILL ISOLATE CARRYING OUT HIS DUTIES, THAT SO FAR HE HAS NOT SHOWN SIGNS OF A FEVER, AND HE HAS TAKEN AN INITIAL DOSE OF PAXLOVID. PRESIDENT BIDEN HAS TESTED POSITIVE FOR COVID THIS AFTERNOON. THE SYMPTOMS ARE SAID TO BE MILD, AND HE HAS NOT BEEN HOSPITALIZED. THAT NEWS FOLLOWING A NEW AND PROMINENT CALL FOR PRESIDENT BIDEN TO EXIT THE 2024 RACE. FROM CALIFORNIA DEMOCRAT SENATE CANDIDATE ADAM SCHIFF FROM C DEMOCRAT SENATE CANDIDATE ADAM SCHIFF WHO WRITES, I BELIEVE IT IS TIME FOR HIM TO PASS THE TORCH. SCHIFF TOLD DONORS LAST WEEKEND, I THINK IF HE IS OUR NOMINEE, I THINK WE LOSE. SCHIFF IS THE 19th DEMOCRATIC LAWMAKER TO URGE THE PRESIDENT TO STEP ASIDE. THOSE CALLS HAVE GROWN QUIET AFTER THE TRUMP ASSASSINATION ATTEMPT. THE PRESIDENT DOES MAINTAIN SUPPORT FROM PROGRESSIVES LIKE BERNIE SANDERS AND THE CONGRESSIONAL BLACK CAUCUS, BUT IN A NEW DEVELOPMENT, DEMOCRATIC LEADERS CHUCK SCHUMER AND HAKEEM JEFFRIES TOGETHER URGED THE DNC TO DELAY ITS VIRTUAL ROLL CALL VOTE THAT WOULD FINALIZE PRESIDENT BIDEN AS THE PARTY NOMINEE. PARTY OFFICIALS CONSIDERED HOLDING THAT ROLL CALL AS EARLY AS NEXT WEEK, BUT NOW SAY THEY WILL ACT BY AUGUST 7th. LAST NIGHT THE PRESIDENT SAYING WHAT WOULD MAKE HIM LEAVE THE RACE. >> IF I HAD SOME MEDICAL CONDITION THAT EMERGED. >> Reporter: ALSO NEW TONIGHT, AFTER PAUSING TELEVISION ADS FOLLOWING THE ASSASSINATION ATTEMPT, THE BIDEN CAMPAIGN IS GOING BACK ON AIR ON ABORTION RIGHTS. >> TRUMP AND JD VANCE DON'T CARE ABOUT WOMEN. >> Reporter: THROUGH A YOUNG WOMAN'S PERSONAL STORY. THE AD NAMES MR. TRUMP'S NEW RUNNING MATE, WHO HAS PREVIOUSLY SPOKEN AGAINST EXCEPTIONS FOR RAPE AND INCEST, BUT SUPPORTS THE TRUMP POSITION THAT STATES DECIDE. TODAY IN BATTLEGROUND MICHIGAN, VICE PRESIDENT HARRIS CALLED OUT VANCE'S VIEWS. >> THIS IS A FELLOW WHO IN THE UNITED STATES SENATE PARTICIPATED IN BLOCKING PROTECTIONS FOR IVF AND HAS MADE EVERY INDICATION THAT HE IS FOR A NATIONAL ABORTION BAN. >> Reporter: KELLY O'DONNELL, NBC NEWS, THE WHITE HOUSE. >>> AND TONIGHT HERE IN MILWAUKEE, THE SPOTLIGHT WILL BE ON OHIO SENATOR JD VANCE AND AFTER A STUNNING POLITICAL RISE, THE 39-YEAR-OLD WILL SPEAK TONIGHT IN PRIME TIME IN HIS ROLE AS FORMER PRESIDENT TRUMP'S RUNNING MATE. HALLIE JACKSON HAS MORE. ♪♪ >> Reporter: TONIGHT, THE FIRST FORMAL CAMPAIGN EVENT FROM THE NEW REPUBLICAN VICE PRESIDENTIAL NOMINEE AT A GOP FUND-RAISER. >> DONALD TRUMP GOT SHOT, AND HE TONED DOWN THE TEMPERATURE. THAT'S WHAT A REAL LEADER DOES. >> Reporter: SENATOR JD VANCE LOOKING AHEAD TO HIS PRIMETIME SPEECH. >> I JOKE WITH THE PRESIDENT THAT, YOU KNOW, I'M VERY EXCITED ABOUT THIS EVENING, AND I DON'T PLAN TO SCREW IT UP, BUT IF I DO, IT'S TOO LATE. HE MADE THE PICK, RIGHT? IT'S OFFICIAL NOW. >> Reporter: THE FIRST-TERM SENATOR WHO TURNS 40 NEXT MONTH ROSE TO PROMINENCE WITH "HILLBILLY ELEGY." >> YOU GET AWAY WITH THIS EVERY TIME. >> I TOLD YOU THAT I WOULD DO BETTER. >> YOU ALWAYS SAY THAT. YOU'RE LYING. >> Reporter: HIS BEST-SELLING MEMOIR TURNED INTO A NETFLIX MOVIE DESCRIBING HIS CHILDHOOD RAISED IN POVERTY BY HIS GRANDPARENTS. VANCE LATER DEPLOYED TO IRAQ WHILE IN THE MARINES AND ON TO YALE LAW SCHOOL AND A BUSINESS CAREER BEFORE RISING TO THE SENATE IN 2022. A SOURCE FAMILIAR WITH VANCE'S REMARKS TONIGHT SAY HE'LL CONNECT HIS LIFE EXPERIENCES TO CAMPAIGN ISSUES LIKE THE IMPACT OF INFLATION, TRADE, AND THE FENTANYL CRISIS. A FORMER TRUMP >> I'M A NEVER TRUMP GUY. I NEVER LIKED HIM. >> Reporter: -- VANCE EVOLVED INTO AN OUTSPOKEN TRUMP SUPPORTER. NOW SEEN AS THE HEIR TO THE MAGA MANTLE. ON POLICY, HE'S A LEADING GOP VOICE AGAINST FUNDING UKRAINE IN ITS WAR WITH RUSSIA AND HE'S BACKED FORMER PRESIDENT TRUMP'S ELECTION FRAUD LIES, SUGGESTING IF HE WERE VICE PRESIDENT, HE WOULD NOT HAVE CERTIFIED THE 2020 ELECTION, DOWNPLAYING THE JANUARY 6th ATTACK. >> I'M EXTREMELY SKEPTICAL THAT MIKE PENCE'S LIFE WAS EVER IN DANGER. >> Reporter: AND IN 2021 SUGGESTING SWEEPING CHANGES THAT WOULD INSTALL MORE LOYALISTS IN THE FEDERAL GOVERNMENT. >> FIRE EVERY SINGLE MIDLEVEL BUREAUCRAT, EVERY CIVIL SERVANT IN THE ADMINISTRATIVE STATE, REPLACE THEM WITH OUR PEOPLE. >> Reporter: VANCE NOW OFFICIALLY ON THE GOP TICKET AND IN THE STANDS WITH MR. TRUMP EACH NIGHT OF THE CONVENTION SO FAR. FORMER PRESIDENT TRUMP IS PREPARING FOR HIS OWN SPEECH TOMORROW NIGHT, BUT YOU CAN SEE HIM ACTUALLY HERE ON STAGE TODAY GETTING READY, GETTING A LOOK AT THE LAYOUT. HIS EAR STILL BANDAGED AND THAT'S AFTER LAST NIGHT HE CAME TO THE CONVENTION HALL EARLIER THAN EXPECTED ACCORDING TO A SOURCE FAMILIAR WITH HIS PLANS TO WATCH HIS FORMER RIVALS MAKE THE CASE FOR A SECOND TRUMP TERM. FROM FLORIDA GOVERNOR RON DeSANTIS -- >> AMERICA CANNOT AFFORD FOUR MORE YEARS OF A "WEEKEND AT BERNIE'S" PRESIDENCY. >> Reporter: -- TO FORMER U.N. AMBASSADOR NIKKI HALEY. >> DONALD TRUMP HAS MY STRONG ENDORSEMENT, PERIOD. [ CHEERS AND APPLAUSE ] >> Reporter: BOTH THE SUBJECT OF TRUMP INSULTS DURING THE PRIMARY. >> RON HAS ALWAYS BEEN A LOSER. BIRD BRAIN, YOU KNOW WHO BIRD BRAIN IS, RIGHT, NIKKI. >> Reporter: NOW FIRMLY BEHIND THE PARTY'S LEADER. >> YOU DON'T HAVE TO AGREE WITH TRUMP 100% OF THE TIME TO VOTE FOR HIM. >> AND, HALLIE, WE'RE ALSO EXPECTED TO SEE MORE TRUMP FAMILY MEMBERS FOR THE FIRST TIME HERE. >> Reporter: YEAH, THAT'S RIGHT, LESTER. MULTIPLE SOURCES TELL NBC NEWS THAT MELANIA, IVANKA TRUMP, AND JARED KUSHNER ARE EXPECTED TO APPEAR TOMORROW, PROBABLY IN THE VIP BOX RIGHT THERE, AND WE JUST LEARNED MOMENTS AGO FORMER PRESIDENT TRUMP HIMSELF IS EXPECTED TO APPEAR TONIGHT TO WATCH HIS RUNNING MATE'S SPEECH. LESTER. >> ALL RIGHT, HALLIE, THANKS. I WANT TO BRING IN KRISTEN WELKER, THE MODERATOR OF "MEET THE PRESS." FOR MANY AMERICANS THIS WILL BE THEIR INTRODUCTION TO VANCE. >> IT'S A MAJOR MOMENT FOR VANCE. AS FOR FORMER PRESIDENT TRUMP, WHO CLEARLY MADE THIS DECISION FROM WHAT HE BELIEVES IS A POSITION OF STRENGTH, GIVEN HE HAS A NARROW LEAD IN NATIONAL AND BATTLEGROUND STATE POLLS. VANCE IS VIEWED AS THE FUTURE OF THE MAGA MOVEMENT AND ENERGIZES THE TRUMP BASE BUT DOESN'T EXACTLY EXPAND IT, ALL OF THAT UNDERSCORING WHAT WE'RE SEEING AT THIS CONVENTION SO FAR. THIS IS A PARTY THAT IS REMARKABLY UNIFIED AROUND MR. TRUMP. COMPARE THAT TO THE DIVIDED DEMOCRATS, PRESIDENT BIDEN FACING ANOTHER CALL TO DROP OUT AND A NEW POLL TODAY SHOWING 65% OF DEMOCRATS WANT THE PRESIDENT TO STEP ASIDE. ALL OF IT ADDING TO A REALLY COMPLICATED MIX FOR PRESIDENT BIDEN WHO, OF COURSE, AS WE LESTER, IS NOW BATTLING COVID. >> ALSO THIS MAJOR HEADLINE TONIGHT ABOUT DEMOCRATIC SENATOR BOB MENENDEZ. >> THAT'S RIGHT. THIS IS DEFINITELY A BIG HEADLINE. ONE DAY AFTER HE WAS FOUND GUILTY ON ALL COUNTS IN A CORRUPTION TRIAL, TWO SOURCES TELL US HE'S BEEN PHONING HIS SENATE COLLEAGUES SAYING HE DOES, IN FACT, INTEND TO RESIGN AMID CALLS FOR HIM TO DO SO. >> ALL RIGHT, KRISTEN WELKER, THANKS VERY MUCH. >>> JOIN ME AND SAVANNAH GUTHRIE AS JD VANCE ADDRESSES THE CONVENTION WITH COVERAGE KICKING OFF AT 9:00 P.M. EASTERN. >>> WE'RE LEARNING NEW DETAILS ABOUT THE ATTEMPTED ASSASSINATION OF FORMER PRESIDENT DONALD TRUMP AND WHAT THE SECRET SERVICE KNEW IN THE MINUTES BEFORE SHOTS WERE FIRED. STEPHANIE GOSK HAS LATE DETAILS. >> Reporter: IN AN FBI AND SECRET SERVICE BRIEFING WITH MEMBERS OF THE SENATE, TROUBLING REVELATIONS ABOUT THE HOUR BEFORE A 20-YEAR-OLD GUNMAN OPENED FIRE ON FORMER PRESIDENT DONALD TRUMP. SENATORS LEARNED THAT HE WAS IDENTIFIED AS BEING SUSPICIOUS AND PHOTOGRAPHED MORE THAN AN HOUR BEFORE THE SHOOTING. ACCORDING TO MULTIPLE SOURCES FAMILIAR WITH THE BRIEFING, A DETAILED TIME LINE WAS SHARED WITH SENATORS. AT 5:51 P.M., PENNSYLVANIA STATE POLICE NOTIFIED SECRET SERVICE OF A SUSPICIOUS PERSON WITH A RANGE FINDER. 5:53, THE SECRET SERVICE NOTIFIED ITS SNIPERS. AT 6:02, TRUMP TAKES THE STAGE. >> HE'S ON THE ROOF. >> Reporter: AT 6:09 PEOPLE IN THE CROWD SAW THOMAS CROOKS ON THE ROOFTOP AND SHOUTED TO LAW ENFORCEMENT. >> RIGHT HERE. >> Reporter: AND TWO MINUTES LATER, SHOTS ARE FIRED. SENATOR RON JOHNSON REACTING TO THE BRIEFING AT THE REPUBLICAN CONVENTION IN WISCONSIN TODAY. >> CONGRESS HAS GOT TO DO DETAILED AND INTENSIVE OVERSIGHT AND LEAVE NO STONE UNTURNED, NO QUESTION UNASKED OR UNANSWERED. >> Reporter: SENATORS ALSO LEARNED THE SHOOTER VISITED THE RALLY SITE SEVERAL DAYS IN ADVANCE OF TRUMP'S APPEARANCE TO SCOPE IT OUT. >> IT WAS A COVER YOUR ASS BRIEFING BY THE SECRET SERVICE. THE DIRECTOR OF THE SECRET SERVICE NEEDS TO GO. >> Reporter: TODAY, A SECRET SERVICE SPOKESMAN TOLD NBC NEWS A LOCAL S.W.A.T. TEAM WAS POSITIONED IN THE COMPLEX WHERE CROOKS FIRED THE SHOTS, BUT NOT IN THE SAME BUILDING. >> WOULD ONE OF THE GOALS OF A TEAM SECURING THAT AREA BE TO KEEP PEOPLE OFF THE ROOF? >> FOR SURE. THE PLAN, WHATEVER IT WAS, FAILED, AND WE NEED TO UNDERSTAND WHY. >> Reporter: TONIGHT, PRESSURE IS MOUNTING ON THE SECRET SERVICE IN THE WAKE OF THESE REVELATIONS. TRUMP WAS ALLOWED TO TAKE THE STAGE EVEN THOUGH A SUSPICIOUS INDIVIDUAL WAS SPOTTED IN THE AREA. >> MAYBE HE'S CARRYING A RANGE FINDER BUT NOT A REPORT OF A WEAPON. YOU WOULD NOT NECESSARILY BE CONSIDERING MOVING YOUR PROTECTEE OR DELAYING HIS ENTRANCE ONTO THE STAGE. >> Reporter: SENIOR LAW ENFORCEMENT OFFICIALS SAY CROOKS WAS ALSO FOUND WITH THIS DEVICE, A FIREWORKS DETONATOR. FEDERAL AGENCIES SAID SUSPECTED IMPROVISED EXPLOSIVE DEVICES WERE IN HIS CAR. THE DEPARTMENT OF HOMELAND SECURITY INSPECTOR GENERAL NOW OPENING AN INVESTIGATION INTO THE AGENCY'S HANDLING OF SATURDAY'S RALLY. AMONG THE MANY UNANSWERED QUESTIONS, WHEN DID LAW ENFORCEMENT FIRST SEE THE GUN? >> AND, STEPHANIE, AS THESE NEW DETAILS COME IN, ARE WE LEARNING ANYTHING MORE ABOUT THE SHOOTER'S MOTIVE? >> Reporter: LESTER, FBI DIRECTOR CHRISTOPHER WRAY SAYS THEY HAVE INTERVIEWED 200 PEOPLE. THEY HAVE SCOURED THE SHOOTER'S ELECTRONIC DEVICES, AND THEY ARE NO CLOSER TO UNDERSTANDING A MOTIVE. LESTER. >> ALL RIGHT, STEPHANIE GOSK, THANK YOU. >>> NOW TO THE DIRE AFTERMATH OF A DANGEROUS STORM THAT BARRELED THROUGH PARTS OF THE SOUTH, AND NOW THAT SAME SYSTEM IS ON THE MOVE NORTH WITH MORE THAN 50 MILLION PEOPLE IN ITS PATH. GUAD VENEGAS JOINS US FROM THE WASHED OUT OZARKS. GUAD, GOOD EVENING. >> Reporter: LESTER, MANY SURPRISED BY THE FLASH FLOODS INCLUDING A DRIVER WHO WAS ON THIS BRIDGE ON THE WAY TO WORK AND WAS WASHED AWAY. THAT DRIVER LATER RESCUED BY AUTHORITIES. RUSHING WATERS IN THE ARKANSAS' OZARKS -- >> IT'S FLOODED OVER THERE, BOYS. >> Reporter: -- CREATING A FLASH FLOOD EMERGENCY OVERNIGHT. MORE THAN 80 SENIORS EVACUATED FROM THIS ASSISTED LIVING FACILITY IN THE CITY OF YELVILLE. THIS CREEK RISING IN JUST MINUTES FORCING SOME PATIENTS TO HOLD ON TO THEIR MATTRESSES AS THE WATER ROSE ACCORDING TO A SPOKESPERSON. NEARBY ROADS AND BRIDGES LEFT TORN APART. >> YOU DON'T REALIZE HOW SCARY IT IS UNTIL YOU ARE IN THAT MOMENT. >> Reporter: THE FAST-MOVING WATERS MOVING THIS HOME RIGHT OFF THE FOUNDATION AND CRUSHING THIS CARPORT. >> I'M SO THANKFUL THAT EVERYBODY IS STILL ALIVE. >> Reporter: TODAY FOR BUSINESS OWNERS LIKE GLEN ADAMS, THE CLEANUP IS UNDER WAY. >> THERE'S JUST A WALL OF WATER. >> Reporter: THE HEAVY RAIN PART OF A HEAT-BREAKING COLD FRONT THAT TRIGGERED STORMS ACROSS THE SOUTH AND LEAVES 54 MILLION AT RISK OF SEVERE WEATHER THIS EVENING. A RARE TORNADO IN ROME, NEW YORK, KNOCKING THE STEEPLE OFF THIS CHURCH AND INTO THE BUILDING'S ROOF, CARS CRUSHED. ONE MAN DIED AS HE WAS SWEPT AWAY BY FLOODWATERS. >> HE WAS WAS OUT THERE LIVING LIFE AS ONE DOES AND UNEXPECTEDLY SWEPT FROM US. >> Reporter: AS THE SUMMER OF SEVERE WEATHER LEAVING MILLIONS BRACING FOR ANOTHER ROUND TONIGHT. GUAD VENEGAS, NBC NEWS. >>> IN 60 SECONDS, THE POSSIBLE MURDER MYSTERY INVOLVING THE POISONING OF AMERICANS AT A LUXURY HOTEL IN THAILAND. >>> WE'RE BACK WITH THE INTERNATIONAL INVESTIGATION INTO THE DEATHS OF SIX PEOPLE INCLUDING TWO AMERICANS AT A LUXURY HOTEL IN THAILAND. JANIS MACKEY FRAYER REPORTS, THEY FOUND TRACES OF CYANIDE. >> Reporter: A SHOCKING CASE AT A FIVE-STAR HOTEL IN BANGKOK INVOLVING SIX BODIES INSIDE A LOCKED ROOM. THAI POLICE DESCRIBING A SCENE WITH DISHES OF UNTOUCHED FOOD AND TRACES OF CYANIDE FOUND ON CUPS AND A TEAPOT. ONE OF THE PEOPLE THEY SAY APPEARING TO POISON THE OTHERS. INVESTIGATORS SAID THE VICTIMS, THREE MEN, THREE WOMEN, AGES 37 TO 56, WERE FOUND IN DIFFERENT AREAS OF THE SUITE WITH NO SIGNS OF STRUGGLE, ALL OF VIETNAMESE DESCENT, TWO OF THEM U.S. CITIZENS. THAI POLICE SAY THE FBI IS ASSISTING WITH THE INVESTIGATION. >> WE OFFER OUR SINCERE CONDOLENCES TO THE FAMILIES ON THEIR LOSS. WE ARE CLOSELY MONITORING THE SITUATION. >> Reporter: ACCORDING TO POLICE, FOUR OF THE VICTIMS HAD INVESTED MONEY TOGETHER, RAISING SPECULATION OF A DISPUTE OVER DEBT. THESE IMAGES RELEASED BY THAI POLICE SHOW SOME OF THEIR LAST MOMENTS ALIVE ENTERING THE HOTEL. OFFICIALS SAY A ROOM SERVICE ORDER WAS LATER DELIVERED. WHO USED THE CYANIDE AND WHY REMAINS A MYSTERY. THE BODIES FOUND TUESDAY BY A HOTEL MAID WHEN THE GUESTS DIDN'T CHECK OUT. >> THE NEXT STEP IS LOOKING AT ALL OF THE RELATIONSHIPS OF ALL THE VICTIMS TO EACH OTHER AND OTHERS TO SEE WHETHER OR NOT ANYONE HAD A MOTIVE TO KILL THEM. >> Reporter: THAILAND'S PRIME MINISTER RUSHED TO THE HOTEL TO ASSURE TOURISTS THAT THE COUNTRY REMAINS SAFE. JANIS MACKEY FRAYER, NBC NEWS, BEIJING. >>> AND UP NEXT FOR US TONIGHT, NFL HALL OF FAMER TERRELL DAVIS SPEAKS OUT AFTER HE WAS HANDCUFFED ON A FLIGHT FOR REASONS HE SAYS HE STILL DOESN'T UNDERSTAND. HIS POWERF >>> BACK NOW WITH OUR INTERVIEW WITH TERRELL DAVIS, THE NFL HALL OF FAMER WHO WAS REMOVED FROM A UNITED FLIGHT IN HANDCUFFS IN FRONT OF HIS FAMILY. HE'S SPEAKING TO OUR YASMIN VOSSOUGHIAN. ABOUT WHAT HE CALLS A HUMILIATING INCIDENT. >> Reporter: TONIGHT NFL HALL OF FAMER TERRELL DAVIS DEMANDING ACCOUNTABILITY AFTER HE SAYS HE WAS HANDCUFFED AND REMOVED FROM A UNITED AIRLINE FLIGHT. >> MY SON POLITELY ASKED, EXCUSE ME, MAY I PLEASE HAVE A CUP OF ICE, AND SO I PUT MY HAND UP LIKE, AND HE DIDN'T SEE IT. SO I REACHED AND TAPPED HIM ON HIS SHOULDER, AND THAT'S WHEN HE SWUNG BACK AND SAID, DON'T HIT ME, AND I -- I'M A LITTLE CONFUSED. I DIDN'T HIT YOU. >> Reporter: THE BRONCOS LEGEND TRAVELING TO CALIFORNIA WITH HIS WIFE TAMIKO AND THREE KIDS WHEN THEY LANDED, HE SAID. THE PILOT ASKED ALL PASSENGERS TO REMAIN SEATED. THEN ACCORDING TO DAVIS, SIX FBI AND LAW ENFORCEMENT OFFICERS BOARD THE PLANE. >> THEY COME RIGHT TOWARDS ME, AND AT THAT POINT MY MIND IS, LIKE, WHAT THE HECK IS GOING ON? I'M IN SHOCK THAT THIS GUY IS ACTUALLY PUTTING HANDCUFFS ON ME. >> Reporter: HIS THREE CHILDREN WERE LOOKING ON. >> I WAS POWERLESS. I COULDN'T DO ANYTHING. >> AND OUR KIDS, THEY WERE HELPLESS. YOU KNOW, IT WAS THE ABSOLUTE MOST HORRIFYING EXPERIENCE OF MY LIFE. >> Reporter: DAVIS SAID HE WAS QUESTIONED FOR WHAT FELT LIKE 45 MINUTES. >> THEY APOLOGIZED, TALKED ABOUT HOW THIS WAS NOT WHAT THEY HAD GOTTEN, YOU KNOW, REPORTED. >> Reporter: THE FBI TELLING NBC NEWS THEIR AGENTS WERE RESPONDING TO A REPORT OF A VIOLENT ASSAULT. >> DID YOU FEEL AS IF YOU WERE RACIALLY PROFILED ON THAT FLIGHT? >> YEAH, I FELT LIKE THAT PLAYED A ROLE. >> Reporter: UNITED AIRLINES SAID IN A STATEMENT, IT HAS REMOVED THE FLIGHT ATTENDANT FROM DUTY WHILE IT INVESTIGATES. THIS IS CLEARLY NOT THE KIND OF TRAVEL EXPERIENCE WE STRIVE TO PROVIDE, AND WE HAVE REACHED OUT TO MR. DAVIS' TEAM TO APOLOGIZE, BUT TERRELL AND TAMIKO DAVIS SAY THEY'RE NOW LEFT TRYING TO HELP THEIR KIDS PROCESS WHAT HAPPENED TO THEIR DAD. >> UNFORTUNATELY, BECAUSE OF THE BEAUTIFUL COLOR OF YOUR SKIN, YOUR EXPERIENCES IN THIS WORLD ARE GOING TO BE DIFFERENT, AND, UNFORTUNATELY, AT 13, 11, AND 9, YOU'VE HAD AN EXPERIENCE. >> TERRELL, IF THE FLIGHT ATTENDANT WAS SITTING IN THE SEAT THAT I'M IN RIGHT NOW, WHAT WOULD YOU SAY TO HIM? >> I WOULD WANT TO KNOW WHY, WHY WOULD YOU WANT TO RUIN A MAN'S LIFE LIKE THAT, AND I WANT HIM TO ANSWER THOSE QUESTIONS IN FRONT OF MY CHILDREN, LIKE, LOOK THEM IN THE EYES, AND TELL THEM WHY THEY TRIED TO HARM, DESTROY THEIR DAD. >> Reporter: YASMIN VOSSOUGHIAN, NBC NEWS, NEW YORK >>> UP NEXT AS WE CONTINUE HERE TONIGHT, >>> FINALLY, SWIMMING HASN'T BEEN ALLOWED IN >>> FINALLY, SWIMMING HASN'T BEEN ALLOWED IN PARIS' RIVER SEINE FOR A CENTURY. TODAY AHEAD OF THE OLYMPICS THE MAYOR OF THE CITY OF LIGHT TOOK THE PLUNGE. HERE'S REHEMA ELLIS. [ CHEERS ] >> Reporter: IT'S THE DIVE INTO THE SEINE RIVER THAT PARIS' MAYOR HAS BEEN DREAMING ABOUT TO SHOW THE WATER IS CLEAN. >> IT'S AMAZING. WE WORK A LOT AND VERY HARD FOR THAT VERY LUCKY AND HAPPY DAY. >> Reporter: HAPPY BECAUSE THE SEINE WILL BE THE CENTERPIECE OF THE OLYMPICS. IN LESS THAN TWO WEEKS FROM NOW, OPENING CEREMONIES WILL BE HOSTED ON THE RIVER FOR THE FIRST TIME, BUT THERE HAD BEEN CONCERNS ABOUT ATHLETES COMPETING IN THE WATER. THE RIVER IS SO POLLUTED, SWIMMING IN THE SEINE WAS BANNED FOR MORE THAN A CENTURY WITH ONLY A FEW EXCEPTIONS. DETERMINED TO MAKE IT SAFE AGAIN FOR THE OLYMPICS, CLEANUP EFFORTS BEGAN OVER NINE YEARS AGO COSTING $1.5 BILLION. IT INCLUDED A GIANT UNDERGROUND WATER STORAGE BASIN, RENOVATING SEWER LINES AND TREATMENT PLANTS. EVEN WITH ALL THAT, WATER QUALITY TESTS LAST MONTH INDICATED MORE NEEDED TO BE DONE. IT'S NOT THE FIRST TIME A CITY HAS PUSHED PREPARATIONS FOR OLYMPIC GAMES RIGHT UP TO THE BRINK. IN RIO, THE WATER QUALITY WAS ALSO IN DOUBT FOR BOATING EVENTS, BUT THE ISSUES WERE RESOLVED JUST IN TIME. BACK IN PARIS -- >> WE DID IT. WE DID IT. >> Reporter: -- OFFICIALS SAY THE LATEST WATER QUALITY TESTS SHOW WELCOMED IMPROVEMENTS, AND PARIS IS READY TO LET THE GAMES BEGIN. REHEMA ELLIS, NBC NEWS. >> THAT IS "NIGHTLY NEWS" FOR THIS WEDNESDAY. THANK YOU FOR WATCHING. I'M LESTER HOLT. PLEASE TAKE CARE OF YOURSELF AND EACH OTHER. GOOD NIGHT.