tonight, relentless disaster. 20,000 rescues as floodwaters carve a deadly path of destruction. emergency shelters packed as we see the mammoth scale of devastation. residents running for their lives as homes burn t firefighters unleash a massive attack. extreme vetting. donald trump's new ideological test for immigrants, what he said today about allowing only people who support our values to enter the u.s. trapped by war. richard engel with a report inside aleppo, treating syria's children who fill bed after bed.

and simone biles wins another gold. are they the best athletes of all-time? "nightly news" from rio begins right now. >> announcer: this is nbc "nightly news with lester holt" reporting from the olympic summer games in rio. from the olympics, first the headlines. at least seven deaths have now been reported in louisiana. the number of rescues has reached 20,000 after a staggering amount of rain, as much as 2 1/2 feet inside 72 hours in some places. from overhead, baton rouge this evening, we're looking at a watery scene that is in some ways reminiscent of the

gabe. >> reporter: now a federal disaster area. >> what are we looking at right here? >> a shopping center, clearly a major retail area. >> reporter: today a break from the downpours, but not from the heart break. many rivers receding, but still at have been rescued in louisiana in the past few days, more than 12,000 or so have spent time in emergency shelters. life after the historic flood won't be the same. in the hard hit town of watson, after 34 inches of torrential rain, the loss is staggering. >> basically we lost everything other than our lives. >> reporter: mark mccully barely escaped with his wife and kids as the river rose

hours, we probably had six foot of water. water is probably one of the worst mother nature beasts there is. >> reporter: his son with his own rescue story. rescued by a helicopter just in time. now the tropical moisture spreading west and north, putting 20 million people in six states under flood watches, parts of missouri and texas have already flooded. >> it's acting just like a tropical system without the wind. it's grabbing all of gulf of mexico and continues to drop it as torrential rain along the gulf coast. >> reporter: in louisiana, communities cut off for days are assessing the unthinkable damage. pastor michael luce's church where homeowners sought sanctuary as homeowners were trapped on the second floor. tonight he is grateful to be alive. adding to the disaster, many homes are not covered by

recede, major roads are shut down and a bit more rain is in the forecast through wednesday. >> gabe, we're watching another terrible disaster of a very different kind. it's unfolding in the opposite end of the country, in california where firefighters are battling eight large wildfires that are burning, they're being temperatures and dry wind. >> reporter: out of control and burning fast. the so-called clayton fire ripping through main street of lower lake, a town founded in 1858. more than 1,000 firefighters battling flames on the ground. and in the air. leaving wilted skeletons of homes and

flames coming, it was right here. it just come so fast. >> reporter: as these 175 structures decimated across 4,000 acres. >> the devastation is huge, the devastation is extensive and there are hundreds of homes and buildings and structures that have been lost as a result of the fire yesterday. >> reporter: the local building warehouse up in flames now reduced to charred had gone off. >> reporter: jody barnes has lefted in lower lake for more than 20 years. >> grabbed the cats and grabbed the dog and basically ran for our life. >> reporter: all this devastation just a few miles from the historic valley fire last year. it was the third worst fire every in california. >> it's the last thing we wanted to have happen, really it's just tragic. >> reporter: up here

the air smells of ash. the fire still very much on the move, just 5% contain and the cause still unknown. and the late day winds are picking up and this could send the fire in new directions and fast. lester? here in rio, a lot of news to cover, both on and off the field of play, a scare at the olympic park outside the basketball venue when a tv camera from the olympic fell 60 feet from a cable above that snapped. seven people were injured and also two fires burning a few miles from the olympic field venue that kicked up smoke and ash and landed on the venue. and a pair of athletes who just might be the best ever in their respective sports. we get the latest from nbc's stephanie gosk.

seconds, but the usain bolt show just keeps going and going. from the very moment he walked out, to well after the race was over. this is not just about jamaica loving you, it's about the world loving you. why is that? >> it's just my charisma, you know what i mean? >> reporter: yes, it's pretty clear what he means. compare that reaction to this. u.s. sprinter justin gatlin, banned from doping finished second. >> i could see everybody so i was laughing. i knew i was catching him and one thing i always quote, just don't panic, take your time. >> reporter: bolt's start was the second slowest, but then enough ahead to give a cheeky look. usain bolt is unstoppable. at 6'5", he typically

which means each of his strides is nearly 8 feet long, from here to here. now i'm 5'8" and i'm not even close. and i probably can't get up. now bolt has a record three gold in the 100 meter dash. he will race three more times in rio. while in gymnastics, dominance slipped for simone biles. >> if you think about it, i'm the has won as many times as i have. so i have to give myself props for that. >> reporter: instead of gold on the beam, she won bronze. allison felix is going to race in the 100 meter. she's hoping to repeat her gold medal win in london. a busy day on the campaign trail today, donald trump and hillary clinton both

trump unveiled his new immigration proposal, something he called extreme vetting while clinton had some high powered help in going after donald trump. we start with nbc's katy tur. >> reporter: tonight donald trump's message is clear. >> hillary clinton launched isis on to the world stage. >> reporter: under democrats, isis is expanding, under him that will end. trump is outlining new details for his controversial new muslim ban. vetting. >> reporter: the vetting including what trump calls a cold war era ideological test. >> we must screen out any hostile attitudes towards our country. >> reporter: trump also calls for using warning signs for international intervention. >> this new system will be used for local police officers, federal investigators and immigration screeners. >> he's saying a majority of americans

set aside some civil liberties. >> reporter: notably missing trump's past insistence that obama founded isis. it gets repeated in the middle east and puts a target on u.s. troops. >> if my son were still in iraq, and i say to all those who are there, the threat to their life has gone up a couple ic message on isis turned to -- anti-corruption task force uncovered a ledger allegedly documenting $7.12 million in off the books cash payments from ukraine's past from paul manafort. manafort called the allegation silly and nonsensical. >> reporter: this is

going after donald trump where he's strongest, with white working class voters. trump is counting on them to give him his best and perhaps only shot at the white house. joe biden is helping clinton make her case. >> if you're worried about your job, then there's only one person in this election who will possibly help you and that is hillary clinton. >> we're going to make the biggest investm ii. >> reporter: joe biden telling me donald trump's economic plan doesn't add up. >> he has no notion what he's talking about. and just look at his budget. >> reporter: what do you say to white, not college educated men in pennsylvania, in scranton. >> that's what i'm saying here, take a look at the facts, take a look at what he's talking about. >> reporter: clinton is practically camping

democrats held their convention, launched her bus tour, and though polls have her head among white working class voters, trump is up and gaining. so we went to a local coffee house and asked why trump? have you decided who you're going to vote for? >> i'm going to vote for trump because i think he can by jobs back because he's a successful businessman. >> donald trump knows what it is to run a business, he knows how to make the economy grow. >> reporter: clinton with a big dose of joe biden. tonight we have a rare look inside a secret operation saving lives in war torn syria. it's an underground hospital hidden away as the brutal conflict between government forces and rebels wages on above. and so many patients brought here are children. richard engel brought us inside where some of the images may be disturbing to watch.

bombing of aleppo has targeted so many hospitals the few still working have been forced below ground. nbc news was granted rare access to one of these unmarked hidden basement clinics, where 2-year-old bayon was barely alive after an air strike on his home. medical staff tirelessly tried to push and pump life into the boy. then listen for a heart beat that wasn't there. take in the horror, children keep streaming in. after bombings in this city, rescue workers often save children first, so it's children who fill nearly every bed. >> the images never leave you, they scar you. >> reporter: this doctor is a surgeon in chicago, but last month, he snuck into aleppo to volunteer. >> the doctors are exhausted, they're

the world, it's that they want the world to know what's happening. >> reporter: the makeshift hospital rooms are crowded. it can take days for families to find their injured sons and daughters. 10-year-old sawad lost her leg, she had been sleeping by a window when a bomb dropped. the doctor asked if any of her relatives were hurt. she says no, but she's wrong. she doesn't know that the attack that took her leg, also killed her 8-ye brother. a boy nearby repeats, he wants to leave. but there's no leaving aleppo, it's encircled, starving and under attack. the injured children forced under ground. richard engel, nbc news. >> and that nightmare continues. there's more ahead as we continue, violence in the streets, fears of another dangerous night in a major american city where protesters demand to

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st-prescribed biologic. we're back now with tensions erupting in milwaukee, a curfew has now been imposed for teens this week after 14 people were arrested, one person was shot and several officers were injured during protests last night. driving it all, a police officer who shot and killed an alleged armed suspect.

nbc's kerry sanders has more. >> reporter: two rounds of violence, gun fire and destruction in milwaukee and tonight with more fears of unrest, no let up in demand for the body camera footage. the video shows the man running away after a traffic stop, raising what appears to be a gun in his police officer still unnamed firing two fatal shots. >> we want them to release the tape so we can see it. because i these they're hiding something, taking too long. >> reporter: after swearing in 40 new police recruits today, milwaukee's mayor said he too wants that both cam video released. the clip was recorded without audio lasts only 25 seconds. >> i did not see the

video in which the video had a gun in his hand. >> reporter: but which wisconsin state officials say they cannot release the video because it's key evidence in their case against the shooter. police tweeted photos of gunshots fired at them, a police riot helmet hit by a bullet last night. heightened anxiety here tonight as riot police may again have to enter this neighborhood. kerry sanders, nbc news, milwaukee. up next, a new warning about the up next, a new warning about the health risks of [ crowd nois] whoa. [ gears stopping ] when your pain reliever stops working, your whole day stops. try this.

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reconnect with the life you've been missing. get a free sample at depend.com. the rain falling and finally it is one of the wonders of this immense country and indeed the whole world. the amazon rain forest, as big as the continental u.s. and home to more species of animals than anywhere on earth. tom brokaw heads here to take a look at what some call the lungs of the earth. >> reporter: it is a world unto itself, of life where nature

square mile after square mile, one-fifth of all the fresh water in the world. i first traveled to the amazon 25 years ago to see the work of scientists cataloging this treasure house of the natural world. so how many lifetimes would it take for you to know a lot more than you do now about what it's going on here? >> well, you know how it works, the more you know, the more you need to >> reporter: this man and his wife are hid of national am zonian research. >> this is part of the national treasure of the earth, right? >> the forest is very important for a lot of people. >> reporter: prized by scientists and fortune seekers alike. when you're in the rain forest, it has kind of a spiritual effect. but it also has a sinister danger because it's become a

ecologists, naturalists and people who want to develop this area. according to an international human rights organizationization, 24 activists have been killed for their work in the amazon in the first four months of this year alone. the many indigenous tribes are under tremendous pressure here as well. >> there is a feeling that protecting the rain forest and natural ecosystems in the amazon is worksing against that we make it clear that everybody benefits from a preserved ecosystem. >> reporter: a future without the amazon is simply unthinkable. >> we really haven't come close to describing everything there is. this is the michael jordan of biodiversity. >> or lebron james these days. >> right. >> reporter: mario has been upriver for a long time. for him, no man-made wonder can compete with the natural

tom brokaw, nbc news, in the amazon. and that will do it for us on this monday, a reminder, nbc prime time olympic

michael, this is my last interview. >> it's my last interview with you, too. >> this is it! >> i wouldn't change who i am today for anything. >> how does nicole figure in that? >> as one era ends, a beautiful new one neither was a sure thing. michael shares his story of his now or never moment with nicole. >> she probably hated me at that point. she didn't want anything to do with me. >> he cocked it, put to it my forehead. >> the interview with ryan lochte and every shocking detail. and nicole and katie's bond goes beyond the pool. >> ledecky is coming in.