"20/20" tonight. that does it for us here on abc7 news at 5:00, see you at 6:00. tonight, a special edition of "world news tonight." terror in orlando. the worst mass shooting in american history. at least 50 killed. dozens more wounded. the gunman armed with an assault rifle and a handgun, firing at will. hostages held inside. >> oh, my god. >> the s.w.a.t. team in a three-hour standoff. >> we haven't been able to call him or text him. >> the mother in anguish, waiting to hear if her son is still inside. >> breaking details on the shooter. calling 911, pleading his allegiance to isis. we've learned he was interviewed by the fbi three times. and that he bought his guns

legally this past week. and american cities on high alert. as we ask, how many lone wolves is the fbi tracking? our entire team is on this. a special edition of "world news tonight" begins now. good evening. as we come on the air this sunday night, america is just now coming to grips with what unfolded here in the early morning hours, a massacre. at a gay night club in orlando overnight. we learned called 911 to pledge allegiance to isis. >> oh, my god. >> a volley of gunshots in the night, carnage inside, and also outside.

the gunman, omar mateen, was an american born in new york. tonight, we now know he was known to the fbi. and had bought his weapons in just the past few days. kroogsz across america, an emotional respond. and here in orlando, hundreds of people lining up to donate their own blood. you can hear the choppers overhead as we come on. we begin tonight with abc's gio benitez. >> reporter: three hours of terror overnight. multiple shootouts, hostages, a packed nightclub under siege. authorities say omar mateen arrived at pulse orlando, a gay nightclub and bar, armed with an ar-15 assault rifle, a handgun, and an unknown amount of ammunition. by the time it was all over, at least 50 dead, even more injured tonight. the first signs of trouble, just after 2:00 a.m. officers responding to gunfire. at one point, mateen goes outside, where police exchange shots with the suspect. he runs back inside to open fire

again. >> i was just hearing the bang, bang, bang, i thought it was part of a song. there was blood splattering. i didn't know if it was mine or somebody else's. >> reporter: pulse nightclub posting on facebook, everyone get out of pulse and don't stop running. >> they just started shooting, shooting, shooting. everybody dropped to the ground, and started running. >> reporter: dozens now hostages, some huddled in the bathroom. texting to loved ones. nina justice, showing us these ominous messages. mommy, i love you, writes her son. trapped in bathroom. >> please come get us, because he's about to get us. he was going to die, and he loved me. that's the last thing i heard. >> reporter: authorities sending armored vehicles, and s.w.a.t. teams to the scene. then deciding it was time to make their move. >> we're being told possibly up to 15 remaining in the club that are barricaded in. >> reporter: just after 5:00 a.m., s.w.a.t. officers break through the wall of the club, exchanging gunfire with the suspect again.

>> they're shooting back and forth. >> from there, we exchanged gunfire with the suspect, and he was dead at the scene. we rescued about 30 people. >> reporter: this image of the damaged helmet of an officer. injured during the firefight. the aftermath, gruesome. some dead on the street, others carried away. worried relatives rushing to the club. >> my son hasn't been heard from. so, i don't know if he was left in the club, if he got shot, or if he's being worked on here. i don't know. it's terrible. he's my only child. >> reporter: as day breaks, authorities combing through the massive crime scene. >> the amount of bodies that are in there, the amount of victims, it's going to take some time. >> reporter: tonight, that mother still searching for her son. pleading for tolerance. >> when he was in high school, he started the gay/straight alliance. i've been so proud of him for that thing. please, let's all just get along.

we're on this earth for such a short time. let's try to get rid of the hatred and the violence. please. >> the anguish of just one mother tonight. and to think, there are 50 families going through this, not to mention the injured. and the authorities on the scene said you could see it on the face of the officers. who then came out of the nightclub, what they must have witnessed inside. >> it was pure horror. and right now, the deceased are still in there. the victims haven't been identified. mothers, fathers, boyfriends, girlfriends, left with so many questions tonight. we're learning more about the man behind such bloodshed here, omar mateen. he was born in new york, and known to the fbi. had been interviewed by the fbi more than once.

during the mess -- massacre, he called 911 and pledged allegiance to isis. with what we're learning tonight, here's brian ross now. >> reporter: 29-year old omar mateen was well known to the fbi counterterrorism squad. he was interviewed by fbi agents three times over the last three years after he allegedly told co-workers he had ties to known terrorists. >> we determined that contact was minimal and did not constitute a substantive relationship or a threat at that time. >> reporter: there were no criminal charges, and nothing on his record to block his purchase of the two guns he used in the shooting, bought just last week. >> so he can legally walk into a gun dealership and purchase firearms. >> reporter: federal authorities say as mateen was holed up in the orlando nightclub, he called 911. >> announced and pledged his allegiance to al baghdadi, the leader of isis. >> reporter: late today, the isis propaganda news agency claimed that mateen was "an islamic state fighter" although there was no indication the attack was planned by isis. >> this is likely to be someone

that was self-radicalized on the internet and decided the target on his own. >> reporter: mateen was an american citizen, attending high school in stewart, florida, and worked as a security guard. he has a 3-year-old son with his current wife and his ex-wife says he regularly beat her. now, fbi agents are looking for clues. linzie janis outside his apartment. >> investigators are looking for phones, computers, anything that might provide clues. >> reporter: the fbi is also looking closely at mateen's parents, immigrants from afghanistan. this is his father in a rambling diatribe posted on youtube about the afghanistan border. >> and brian, this evening, the shooter's father is speaking out? >> yes, he says his son may have

become upset earlier this month when he saw two men kissing, but says he was as shocked as anyone when he learned what his son had done. david? >> as we learn more about the lone gunman, brian ross will city on this. we want to take you inside the pulse night club. a witness describing what he saw in the terifying moment when the gunman opened fire. >> as i'm getting ready to cash out, out of nowhere, i hear -- it was like an automatic gun. i automatically dropped to the floor, and we heard a second time -- and that's when it started hitting home, this was actually happening. so, i tried to pull everybody down, and people started to smell the ammunition burning. that's when it hit home to everybody, and they realized this was actually happening. people are screaming, crawling on the floor, people started running towards the door. it was complete mayhem, everybody was so nervous, and we wanted to get out. people are getting trampled, we were trying to push everybody out the door.

as i'm escaping the building, i looked around, and people were covered in blood, people screaming, crawling on the floor. it was like a scene out of a horror movie. i was covered in blood, i had lost my shoes. both of my socks were covered in blood. i remember telling myself, this is not how i die. not today. not like this, at least. >> janiel gonzales, who shared his story with us. at this hour, outside the hospital in orlando, the names of the first victims are now being revealed. family and friends keeping vigil all day outside. survivors saying they simply don't know how they made it out alive. here's lauren lyster. >> reporter: a portrait emerging of some of the people caught in the cross-fire this morning. sons, daughters, fathers, boyfriends. juan guerrero, confirmed dead. others, still missing, like jeff

rodriguez, who sent his brother a text from the chaos saying he was bleeding. >> the last text said, i got shot. i'm bleeding out. i think i'm dying, i love you guys, tell mom, dad, everyone, i love them. >> reporter: and dozens more injured, like the bartender at the club. and father of two. josh mcgill stopped to help him. >> he was like, i think i got shot. i took my shirt, said i have to stop the bleeding. i tied it around his arm with my shirt. >> reporter: shot in the back and arms, and in surgery this evening. janet mccoy, escaping the dance floor. her friend shielding her. >> he got shot, and as he felt, everyone was trampling over him, and he broke his leg. i'm only here just because of him.

>> reporter: tonight, he's recovering in the hospital. his family and friends by his side. and this hospital, just down the street from the night club, is where so many of the injured were rushed. 43 being treated tonight, and they're working on reuniting them with their families. david? >> lauren, thank you. police across the country on heightened alert tonight. the fbi and police are now increasing security at the annual pride parade in los angeles. federal authorities struggling to track hundreds of people in the country believed to have sympathized with isis at some point. we've reported on this before. how do you track hundreds of people around the country? the question now, how did this gunman, who had been interviewed by the fbi more than once, slip through the cracks? pierre thomas, with questions for the fbi. >> reporter: tonight, new york city police are on high alert, as authorities fear the

possibility of copycat attacks. >> we have put all the police forces on high alert. there will be extra deployment at places of mass gatherings like this parade. >> reporter: security stepped up on bridges, tunnels and at the world trade center. and at gay pride events across the country. this as the fbi is scrambling to check for any missed leads relating to mateen in an all-out security review. the fbi was already under incredible pressure, tracking as many as 800 isis sympathizers in all 50 states. >> it is a resource and prioritization issue. you are trying to determine which ones require the attention of the agents and task force officers. >> reporter: and today another scare, police arresting a man after finding rifles and explosive materials in his car near the site of the gay pride parade. police adding extra officers along the parade route. our matt gutman was there. >> reporter: after that man was

apprehended, we're told security is beefed up. there are many officers you do see. but there are many undercover officers here that you don't see. >> reporter: the motive unclear but police say there appears to be no ties to the orlando massacre. >> as americans, we will not shrink away, we will not be in our homes, we will not go back into closets. >> pierre thomas, with us live. also in orlando tonight. so many americans watching this are going to be outraged when they hear that the fbi interviewed this lone gunman three times, and nothing showed up that could have predicted this. >> reporter: the great concern is about copycats. the potential someone else will attack. and there's deep worry there's a gaping hole in the national security system. david? >> pierre, thanks.

president said. he's ordered the flags moved to half-staff at this hour. and he addressed the country for the 15th time, calling this both an act of terror, and an act of hate. >> it's a further reminder of how easy it is for someone to get their hands on a weapon that lets them shoot people in a house of worship, a school, a movie theater, or a nightclub. and we need to decide if that's the way we want our country to be. >> let's get to jonathan karl. we talked about this so many times, the frustration in the president's voice. now, the worst mass shooting in american history. >> reporter: the 15th time. he's come out to speak to the nation after a domestic mass shooting. you can see him almost resigned

today, deeply frustrated today. he was very careful, though, not to tie the shooter in orlando to isis or any other radical terrorist group. he will face some tough questions, especially given, as you point out, you had the 911 call where the shooter was pledging allegiance to isis. >> jonathan karl at the white house. thanks so much. and there's much more on this special edition of "world news tonight." coming up, how the presidential candidates responded. donald trump with one message, hillary clinton with an entirely different message. tonight, america getting a look at the candidates, and how they would handle this if they were president. and also, so many scenes like this across the nation. as the nation now mourns. we'll be right back. and played gigs from new york to miami. but i couldn't bear my diabetic nerve pain any longer. so i talked to my doctor and he prescribed lyrica.

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history, donald trump tweeted he's praying for the victims and their families. but then this, appreciate the congrats for being right on radical islamic terrorism. i don't want congrats. i want toughness and vigilance. we must be smart. that tweet setting off a firestorm. meghan mccain, saying you're congratulating yourself? because 50 people are dead? and singer john legend posting, trump is truly an awful person. but trump wasn't done. later, in a statement, if hillary clinton still can't say the two words radical islam, she should get out of the race for the presidency. it's a charge he's made before. >> refuses to even say the words radical islam. refuses to say the words. this alone makes her unfit to be president. >> reporter: but trump's words today, a sharp contrast with clinton's.

who sent out condolences in english and spanish. saying, we need to redouble our efforts to defend the country, and keep guns like the ones last night out of the hands of terrorists and other criminals. clinton was supposed to campaign with president obama on wednesday. that has been postponed. and trump has changed the focus of his speech tomorrow from bill and hillary clinton to isis and the terrorist threat. >> tom llamas, thank you. when we come back, our continued coverage of the terror in orlando. and there's another horrific act in orlando over the weekend -- the shooting of singer christina grimmie. and the emotional scenes like this one, all across the country and right here in orlando. our special edition of "world news tonight" continues in a moment. be the you who shows up in that dress.

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now to another story we're following tonight, here in orlando. the death and the story of a hero brother's tale after his sister was killed in orlando. her name was christina grimmie, from "the voice," she competed on that program. and her brother marcus saying, she loved the lord, and was always there for me. i honestly don't know what i'll do without her. marcus grimmie tackled the shooter friday night, the suspect then turning the gun on himself. and we're also following severe weather across the nation this evening. here are some of the pictures coming in. as you can see, a tornado in montana, destroying several homes. in the heartland, heavy rain and flash flooding forcing water rescues like this one. and this weekend's heat will continue into tomorrow. temperatures topping 90 from texas to the carolinas. in the meantime, the story the whole nation is trying to come to grips with.

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think yotry nexium 24hr.'s best for your heartburn? now the #1 choice of doctors & pharmacists... for their own frequent heartburn. get complete protection with nexium 24 hour. finally tonight here, as this country simply tries to come to grips with what happened here in orlando, emerging now, the story of the brave souls who were inside the night club, that did anything they could to help their friends. tonight, the heroes who stayed behind to help the victims in the aftermath of the horrific nightclub massacre. as the scene unfolded, a parade of the wounded. those well enough to walk, carrying those who could not. those who were hit by the gunfire.

>> so i was helping him, holding his hand, telling him he was going to be okay. it's going to be okay. >> reporter: taking the t-shirts off their backs. using them as tourniquets. as the word spread, devastated friends and family gathering at the scene. at the hospitals, too. waiting to find out if their loved one was one of the 50 dead, and at least 53 wounded. desperate to help hundreds of people. flocked to donate blood, water, food. all of them standing in long lines that stretched for hours today, quietly waiting to offer help, and hope to the victims still fighting for their lives tonight. we thank you for watching here on a sunday night. much more of our reporting from the ground tonight at 10:00 p.m. eastern. i hope you'll join elizabeth and me later tonight. we'll see you then. from all of us here in orlando, thanks for watching. good night.

next at 6:00, the lgbt community targeted in the deadliest mass shooting in u.s. history. how san francisco is responding with the pride parade just weeks away. >> this impacts our partners, our friends, and even some members of our community. >> the bay area's muslim community speaks out about the shoot anything and gunman who says he was inspired by isis. security is tight in san francisco's castro district as people come together to honor those killed in the attack. we begin with terror in orlando. a gunman opens fire in a crowded club, targeting members 0 the lgbt community. 50 people were killed 53 were injured, before police took out the gunman. tonight there is heightened secured in the castro.

thank you for joining, i'm eric thomas. here's the latest. federal investigators say the gunman, 29-year-old omar mateen, called 9-1-1 during the attack and pledged allegiance to isis. his father said he was outraged after seeing two men kiss in miami but the family didn't believe he was very religious. the fbi had interviewed the gunman in 201 -- 2013 good 2014 after he dressed simplety for a suicide bomber. days ago he legally purchased handgun and a long gun. the president called the attack an act of terror and an act of hate. we have coverage on the effect the shooting will have on the pride parade. first, let's go live to sergio quinn tan -- quintana who talked to people mourning. >> reporter: a tragedy that happened across the country but touches the