Transcript for ISIS claims responsibility for deadly Manchester attack

Let's get right to that breaking news. You are looking live at the Manchester arena in England where a suicide bomber set off an explosion in an Ariana grande concert. The concert had just ended when the explosion happened. 20,000 people were there in the arena. So many of them were children in just look at those pictures, young women, young boys, many of them probably going to the first concert of their lives. Here's what we know right now. At least 22 people killed. More than 50 injures and police say another attacker died at the scene. They believe they know who it was and no name released and second arrested. Around 400 police officers deployed overnight with the investigation. Ariana grande spoke out overnight tweeting, broken from the bottom of my heart, I am so, so sorry. I don't have words. It happened right at the end of the concert. Amy flew to Manchester overnight. She's standing by and our team of reporters is tracking every angle starting with our chief attorney correspondent Terry Moran on the scene in Manchester. Good morning, Terry. Reporter: Good morning, George. Manchester is a proud and usually bustling city. This morning it is eerily quiet in shock and grieving for what happened just about a block down there at the Manchester arena. As you say, this morning Manchester police announcing that they have arrested a 23-year-old man in connection with that bombing, this after police confirming last night that they believe one of the dead was the attacker himself as the hunt goes on for who perpetrated this carnage, terror and tragedy. 10:33 P.M. Legal time a blast erupted at the Manchester arena after pop star Ariana grande had closed a sold out concert before 20,000 of her fans. ??? Like everyone was getting up to leave and all of a sudden there was a big bang. Oh, my god. I thought it was gunshots and my life just flashed before my eyes. By the time we got to the top, there was smoke everywhere. There was blood on the floor and you know what it was made out to be. Reporter: As the explosion rocked the arena confusion and pandemonium, people climbing over seats desperate to get out. Smoke is out. Everyone started ten paic. People started streaming out and next thing is a big flash. And then a whoosh of air and then a smell in the air. Everybody is pushing, everybody is shoving, the shoes being lost, phones being dropped in we ran straight out the doors all the way down to the hotel and all I could hear was screaming, people crying. Oh, my god. Reporter: While a P.A. Announcer tried to calm the panicked crowd. Just take your time and keep exiting the building. There is no problems here. Reporter: Outside mayhem as emergency personnel rushed to recover the 22 dead and help the 59 injured. Many concertgoers, mostly teenagers, young girls and their parents covered in blood and shrapnel. Pull it out quickly. Reporter: They were urgently trying to identify the dead man and see if he acted alone or as part of the network. The grief in this city today is palpable. You can feel it because of the nature of this attack on children, teenagers, their parents at a concert just closing at that moment when the tack came and no question that this will scar those people that did survive. Robin. All right, Terry, thank you very much.

This transcript has been automatically generated and may not be 100% accurate.