Transcript for Neighbors identify one suspected assailant in London attack

much. Overnight British police conducting raids in east London. One of the suspects is believed to have lived in that area and we now know ISIS is claiming responsibility for the attack. This morning investigators racing to find out if the attackers were part of a larger terror network. Our chief investigative correspondent Brian Ross is here with those details. Good morning, Brian. Reporter: Good morning, Amy. Authorities this morning say they already know a lot about the plot and the plotters. Officials tell ABC news there's evidence the three terrorists seen in this video before they were killed had been waiting for months to carry out their attack Saturday night and that the trigger may have been this message posted by ISIS just Saturday that called on followers to use vehicles, guns and knives to attack. Work is ongoing to understand more about them, about their connections and about whether they were assisted or supported by anyone else. Reporter: Police moved quickly into that working class east London neighborhood making at least 12 arrests. Many of those arrested were connected to the dead terrorist seen in this photo wearing a fake bomb vest. A vest intended to cause panic and assure martyrdom. Juan way to guarantee becoming martyrs is to wear a suicide vest or what appears to be a suicide vest so the police take lethal action. Reporter: Neighbors told ABC news the dead terrorist is of Pakistani descent, the father of a toddler with a wife who is expecting. Others said they had called police to report him because of his open radical views, even complaining his local mosque was not devout enough. He just said it was not a good mosque. Reporter: With more than 3,000 potential terrorists on British watch lists, authorities say they simply cannot track every suspect or stop every attack. There have been 13 or 14 plots that have been foiled in the last 12 months. And it tells us that this wave out there is beginning to break against Britain and that we've probably got to be prepared for more. Reporter: British authorities say they see no connection between this attack and the attacks at the Manchester concert and the earlier Westminster bridge attack. What they do see is an increased tempo of plots especially with ISIS calling for its followers to attack during the holy month of Ramadan which lasts for two more weeks. Brian, thanks very much. You know, those televised remarks we showed from the president not his first public

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