Cars under water, boats rescuing residents while elsewhere powerful winds level buildings. Nightly news begins right now. Announcer this is nbc nightly news with lester holt, reporting from the Republican National convention in cleveland. Good evening, on the eve of this important convention, the nations attention has once again been aabruptly turned to a heinous act of violence against police. The shooting deaths of three Law Enforcement officers in baton rouge, louisiana, today. Three others were injured including one described tonight as fighting for his life. The officers were shot after they responded to a report of a man with a gun. Police say the shooter was killed. We dont know his motive, but in an acknowledgment of other recent tragedies of violence against police, president obama late today warned against rhetoric and words that divide. Gabe gutierrez is in baton rouge with late details. Reporter the chaos erupted just before 9 00 a. M. Get moving reporter with a panicked call, now all too familiar. Shots fired. Reporter gunfire at a gas station less than a mile from Baton Rouge Police headquarters. Shots fired officer down shots fired, officer down reporter the mayor calling it an ambush and whether officers were lured into a trap is unclear. The subject may be advised. Officer down. Reporter when the gun fight was over, at least three officers dead, three others injured. The suspect wearing black fatigued and armed with a rifle was killed. We think the suspect is down. We have him over there. Were going to check him out with a robot before we lighten up on him. Reporter the shooter identified as gavin long from kansas city, missouri. Its unjustified, its unjustifiable. The violence, the hatred just has to stop. Reporter right now the motive remains unclear. The attack comes less than two weeks with the policeinvolved shooting death of alton sterling, which catapulted baton rouge into the raging National Debate over Law Enforcement tactics. Days later five officers were shot and killed in dallas. Just last week, authorities here announced several arrests connected to stolen guns. At type, police say the weapons may have been part of a plot to kill cops. Late today president obama at the white house only we can prove we have the grace and the character and the common humanity to end this kind of senseless violence. Reporter tonight again another city is in mourning and police are on edge. The officers killed range in ajs from 32 to 45 years old. A sheriffs deputy remains in critical condition. Police say this is no longer an active shooter scenario but this remains a very active scene. At least two people have been taken in for questioning. Gabe, thank you. Lets get more on this investigation and what were learning about the paerpt apparent shooter. We turn to nbcs pete williams. They say they are checking into whether others were involved. Though some say he acted alone. They are still running down leads. They have taken two people in for questioning. Witnesses told police they thought at least two others were involved in the shooting attack but theres no confirmation. So, the question is, who made the 911 call that sdru police to the scene in the first lace . Was it someone who innocently reported seeing a man with a gun or was it someone hoping to lure them there for an ambush. For the man identified as firing the shots is gavin long of kansas city, missouri. Officials say he just turned 29 today. This was his birthday. Police are in the process of searching his house in missouri tonight. Some Law EnforcementOfficials Say they are looking to see if he was associated in the past with a Antigovernment Movement called sovereign sit zns. Followers generally believe local police have no authority. But why baton rouge is the big question tonight. Pete williams for us in our Washington News room, thank you. Its under this shadow of violence at home sxa broad the Republican NationalConvention Kicks off tomorrow here in cleveland. Security is layered and robust around the quicken loans arena. The head of the citys Police Union Says its not enough and called on the governor to take extraordinary weapons to keep people from illegally carrying weapons on the streets here during the convention. Reporter on the eve of the convention, the news out of baton rouge spread fast, the second Deadly Police shooting. Tonight the head of clevela clevelands police union is calling on the governor to declare a state of emergency and suspend ohios open carry law. We need to do something to protect the men and women. Reporter open carry was on display. One gun owner hoped to make a appointment with his assaultstyle rifle. This is to make people aware that there are good people out here. Im not a bad person. Reporter city officials had already said they were altering the security plan following the killing of five officers in dallas. Brian sits on the safety board for the city council. Not only do we have to keep the delegates and, obviously, the candidates safe, but everybody who wears a badge now is a target. Reporter the shooting today is just the latest in a string of incidents in the last year that have shaped clevelands security plan, including multiple violent protests at trump rallies. Just the latest in nice, france. The secret service is in charge here, coordinating 550 Law Enforcement, with Police Officers as far away from california. Interlocking security fences with skon create barriers and cement blocks blocking off streets. The fbi has been gathering intelligence for weeks on possible protests. The owner of this alternative bookstore says seven of his nine employees got home visits from the feds. How did they react to that . Frankly, its always a little upsetting when an Authority Comes to your house and youre like, what did i do . Reporter military leaders are also on hand. A planning document obtained by nbc news shows that 39 colonels are here in an advisory role. More than the number on the ground for the popes visit last year. Today after months and months of planning, clevelands chief of police sounded confident. Its game time. You know, to coin a phrase from the cavs, its game time and were ready. Reporter to give you a sense of how quickly a small group of protesters without a permit can be pretty disruptive. Theyve shut down this street. This is the entrance to where the delegates are heading for a greeting party. They cant meet that greeting until theyre greeted by this force. As for that open carry law, the governor tonight saying he is powerless, he cant suspend it temporarily. Open carry is still in place. Lesser . Quite a show of force behind you. Stephanie goss, thank you. Now to the business at hand as republicans prepare to formally nominate donald trump as their candidate. Our brandnew nbc news wall street journal poll shows trump trailing Hillary Clinton by five points. Thats the same as it was three weeks ago. Donald trump and mike pence still have a bridge divide in their own party. Reporter with balloons in place, the celebration set inside the convention, even as whats happening outside colors the campaign trail yet again. Baton rouge expected to be recognized tomorrow night in cleveland, a senior trump official tells nbc news with donald trump himself calling the country divided and out of control, blaming a lack of leadership. Now hoping to show his party and the world hes ready for the responsibility. This is clearly going to be Donald Trumps convention. The delegates on the floor are going to be his delegates, more importantly the message is going to be his. Reporter that message in a word, unity. But look at the numbers. Nearly 80 of republicans say the party just isnt there, according to our new poll, with trumps unfavorability rating the worst for a presumptive nominee heading into a convention in the history. Poll. Only 38 of Republican Voters say theyre satisfied with him. If the public sees the donald trump that ive gotten to know in private, he will not be stopped. Reporter party head Reince Priebus defending his candidates personality and his most controversial policy. Donald j. Trump is calling for a total and complete shutdown of muslims entering the united states. Reporter today arguing trump has pivoted on his temporary ban on muslims entering the u. S. , even his own vp pick disagrees with him on it. And indiana governor mike pence not a fan of negative campaigning will have to show how hell rk reconcile trumps tone, too. I think this is a good man talking about the issues the American People care about. But name calling. Donald trumps candidacy has been about the issues the American People care about. I call her crooked hillary. Shes crooked hillary. He wont i didnt ask him to do it, but i dont think he should do it because its different for him. Reporter late today here in cleveland, the roll out of the big names set to speak in prime time. The people promoted arent paul ryan or chris christie, its all about friends and family. Six trumps will talk to the delegates gathered here over the next week, lester, perhaps showing that while donald trump may be able to share the spotlight, hes never far from it. Lester . So quiet where you are right now. Certainly wont be that way this time tomorrow. Thank you. Hillary clinton also responding to the Police Killings in baton rouge today, calling it an assault on us all. While the rnc is going on here, shell be on the campaign trail in full force. Our latest polling shows her email scandal is taking a toll on her campaign. We get more on that from nbc. Reporter Hillary Clintons email use still kags a long shadow over voters views of her today. There is evidence they were extremely careless last last fall, only 42 of americans said her private email use as secretary of state was important to their vote. Today our new nbc news wall street journal poll shows thats up to 55 , with trump sure to hit the issue in cleveland, clinton is airing antitrump ads in battleground states. I could stand in the middle of fifth aef and shoot somebody reporter planning to hold five Campaign Events during the conventions first two days. Clinton already getting an assist from senator elizabeth warren. Insecure moneygrubber. Reporter provoking trump with a barrage of tweet this is weekend. Slamming the gop ticket as too small, insecure, weak men. Warren, who trump calls goofy, has been on clintons vp short list. But with trumps running mate, a conventional conservative, some of the pressure on clinton to pick a feisty progressive like warren could be off. Instead she could go with a swing state senator like tim kaine or tom vilsack, whos known her for decades. Ive seen her work and i have seen how she feels, what she feels strongly about. Thats what trust is trust is about results. Reporter clinton working hard to convince voters who say they doubt her honesty, that shes worthy of their trust. Casey hunt, nbc news, washington. Want to turn to chuck todd, nbc news political director and moderator of meet the press. Some say this is a chance for donald trump to assure not only republicans are nervous but the rest. Country hes got this. Will we see that donald trump . If this is a successful week, he almost has to. Look at the point were at. We have a jittery nation. Weve been absorbing all of these some tragedies, some attacks, terrorism. The totality of it makes a public jiltery. You also have a jittery republican party. Not sure if this guy has what it takes. They look at the political opportunity standing in front of them. Look at the piece in our poll on Hillary Clinton, shes very vulnerable. Theyre jittery i thinking this guy is going to blow it. Number one, trying to show the country that he can handle the big moment that is now sitting here right now. You have a jittery nation, he can reassure the nation. He can be the law and order guy, keb the strong, tough guy. At the same time, he has to reassure this crowd he can win. Right now its an uphill battle for both. Well spend a lot of time here. Yes, we will. Great view. Nice view. Thank you. Joining us for nbcs prime time coverage of the Republican National convention. We start tomorrow night at 10 00 p. M. Eastern 7 00 p. M. Time. Turning overseas to the military coup in turkey. Thousands have now been rounded up and arrested as alleged coconspirators. Our chief Foreign CorrespondentRichard Engel has latest from inside turkey. Reporter this is how turkeyments its failed military coup to be remembered. Unarmed civilians standing down tanks, forcing one to frantically retreat over trees. Some confronting a bus of alleged coup plotters. People defending their elected leader, tayyip erdogan. He helped carry a coffin for his campaign manager. More than 6,000 alleged conspirators have already been detained. The traitors will be rooted out like a cancer, promised erdogan, who himself apparently survived a close call. Cnn turk, a local channel, kept broadcasting even as rebel gunmen stormed their studios. There was a single shot that fired inside the building. And thats the casing from that shot. Reporter the chief editor says erdogans jet was harassed by rebels flying f16s. While he was flying into istanbul, we know there were at least two, maybe three f16 fighter jets under rebel control. Reporter in a cockpit recording, a control tower warns erdogans plane about the rebel fighters, which reportedly locked o but never open fire. So tonight a celebrations continue for both the failed coup and the president s survival. Richard engel, nbc news, istanbul. Still ahead tonight, a killers final days. New details on what the attacker in nice, france, was caught on camera doing before killing 84 people. Were back now with new details about the man who carried out the horrific truck attack in nice, france. Police revealing that cameras caught him doing test runs at the location where he ultimately killed 84 people with his truck. We get more from nbcs bill neely. Reporter two more arrests today. French police now questioning six people. Hunting for possible accomplices to mass murder. They released the killers exwife without charge. They now say he Mohamed Lahouaiej bouhlel rehearsed his rampage twice. Cameras recorded him last tuesday and wednesday driving the same rented truck on the same road he took thursday night when he plowed into crowds of people. Survivors, including americans, met today still in shock. The terror of not knowing what was going to happen, the shock was just hell. Like it was just something coming towards me. Then the people were just lying there like rag dolls. He was going totally intentional at high speed, ramming on the people. Reporter of the nearly 300 people bouhlel hit on this rampage along this road, 18 are still on life support. Armed police patrolled nice today, but everyone is asking how can other attacks be stopped . For months Antiterror Police have trained. This drill simulating gunmen attacking a train. In another they battle suicide bombers. But they admit they simply cant prepare for everything. Tonight people spat at the place where the truck driver died and they grieved at the memorials to his helpless victims. Bill neely, nbc news, nice. Were back in a moment with the severe storms millions are dealing with this summer weekend. Were following Severe Weather in several states this evening, especially in North Carolina, where strong storms flooded roadways and prompted some rescues. Nbcs Morgan Ratford has details. Reporter cars under water after floodwater rose 14 feet in just three hours in the parking garage of this North Carolina mall. Waters rose 13 pete in three hours in the parking garage of this North Carolina mall. Flooded roadways, rescue crews trying to help people trapped outside of their homes and inside their cars. I thought i should find somewhere else to stay tonight because its impossible to just go home. I was told that water is pouring into the house, and i dont have no idea whats going on in my house right now. I never saw so much water. The water was up to my knees. My clothes are wet, im freezing. Reporter in the heartland, hail the size of quarters. As heavy rains and 70mileanhour winds left more than 14,000 homes without power this afternoon across iowa. Crews cleaning up mangled metal and uprooted trees, while stunned residents take stock of whats left. Morgan ratford, nbc news, new york. When we come back here tonight, the man whos witnessed over half a century of history here at the grand old party. Finally tonight, finally tonight, its an amazing to think about how much history has been written on Convention Floors just like this one. And few people have been there to witness it in person as many times as a man youre about to meet after more than a dozen of these gatherings. To him its less about the politics and more about the process of how we choose our president s. One of my favorites, of course, is this one from 1976 in kansas city. Reporter mike miller has had a ba backstage pass to this rite of american politics for 52 years. Is there a rhyme or reason as to where states are located . There definitely is. Theres a formula for the states thats based on their political performance. Reporter cleveland marks convention 14 for the 79yearold. He first started coming as a reporter back in 1964. Then in 1972 he started working for the rnc as a behindthescenes operation guy. For miller, conventions are part fascination, part hobby. Over five decades hes amassed a treasure trove 6 memorabilia worthy of a museum. The National Republican meeting in cleveland in 1895. The 1976 contested convention in kansas city remains one of his favorites. President ford won the nomination, only after defeating a strong challenge from ronald reagan. But then some reagan supporters made some noise. They blew those air horns at a key time. They brought the Convention Floor to a standstill. We just had to weather it. Those are now banned by party rules. Reporter among other moments that stick out in millers mind, ray charles bringing down the house in 1984. And this moment in 2012 what do you want me to tell romney . That was a total surprise to me and everyone else. Clint eastwood was backstage. No one knew he was going to do it. He asked one of the contract technical people, do you have a stool . They said, sure. They thought he was going to sit on it. Reporter miller swears this will be his last convention, but keep in mind, hes already retired three times. Theres been so many expectation for this convention. What do you expect here . Well, i dont know. There are always convention moments, defining moments you remember forever. I dont know what theyll be. Reporter you dont know it until you see it. I know there will be one or more, yes, always. The Republican Convention through the eyes of a man who says he hasnt seen it all but he has seen an awful lot 37 well be looking for some of those surprises this week. Thats going to do it for us on a sunday night. Im lester holt. For all of us at nbc news, thank you for watching and good night. Faly d fendof betewsossle r right now on nbc bay area news, the worst possible news for family and friends of a Berkeley Student missing since the truck attack in france. His name now added to the list of victims. The news at 6 00 stars right now. Thank you for joining us. Uc berkeley girled this after that their student was one of those killed in the truck attack in nice. The university released this news earlier today, tragic news. Yes, they received confirmation from the fbi this afternoon. Nicholas leslies