Transcript for ISIS supporters celebrate Manchester attack on concertgoers

We'll get more now on the investigation from our chief investigative correspondent Brian Ross and, Brian, these soft targets, we've seen it time and time again, our greatest vulnerability. Exactly, George. Good morning. At this point no claims of responsibility. But ISIS supporters online are calling it a reason to celebrate and once again an attack aimed at western culture, an attack on a so-called soft target packed with people just out for a good time. It was less than a year ago on a crowded Saturday night at the nightclub in Orlando, Florida, when an ISIS inspired gunman easily got past limited security and opened fire. 49 people died in the worst mass shooting in U.S. History. In Paris, ISIS orchestrated the attack on a soccer stadium. And the Bataclan concert hall where a popular rock band was performing and more than 130 people killed, a perfect target for the terrorists. These are targets that represent western civilization which they see as lascivious, which they see as counter to their very strict version of Islam. Reporter: Both ISIS and Al Qaeda have been posting calls for their followers to attack large gatherings any way they can. Just two months ago there was the attack with a driver mowing down pedestrians on the sidewalk of the parliament bridge in London. And earlier the truck attack in nice, France on bastille day. Oh, my god. Reporter: This morning officials in great Britain say the Manchester attack was a suicide bomb with more planning and sophistication. It could be that there are people who helped this bombmaker make the bomb. That's also possible that an individual could be self-activated B going on the internet and learning how to make the bomb all by himself. Reporter: Among those calling for attacks like those in Manchester is the son of Osama bin laden who is now 28. He is emerging as his father's successor recently telling followers to attack those who transgress what he calls our pure religion including Jews, Americans and those in nato states like great Britain, George. O. Thank you, Brian.

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