Transcript for 1st American victims identified in Sri Lanka attacks
the latest from that terror attack overseas. Authorities are now naming a motive as ISIS also claims responsibility. This as authorities make more arrests. Our foreign correspondent James Longman is there on the scene for us again this morning. Good morning, James. Reporter: Hi, yeah, good morning, robin. As we come on the air we have now had a claim of responsibility by ISIS. It's come through one of their news channels. It's not clear what if any material help they've given but their claim reinforces fears that a foreign network was involved. I'm at saint Sebastian church where more than 100 people died. Blown out windows and doors behind me. Today is a national day of mourning. This country shocked and angry the attacks that could have been stopped. Death looms large over Sri Lanka as the toll from Sunday's suicide attack passes 300 and a nationwide state of emergency remains in effect and memorial services get under way for the victims. At least 40 people have been arrested in connection with the attacks and we're now seeing footage showing a man with a backpack believed to be one of the bombers approaching saint Sebastian church just before the attack. Police investigating. Watch as the man winds his way through the people who would become his victims. Another angle shows him walking by while worshippers play and the moments later the roof blown completely off. Among the victims children of Danish billionaire anders holt it killed three of his four children. The bombings also claiming the lives of at least four American. We mourn the lives of the victim, some were indeed citizens. This is America's fight too. Reporter: The first to be identified dieter Kowalski from Denver standing in line waiting for breakfast when the bomb went off and 11-year-old Kieran shafritz de zoysa from Washington, D.C. His grieving father still in I don't know what's in the mind of a terrorist but they, aim sure, don't know what they they do not know what they took from the world. A brilliant mind who was going to be a neuroscientist and he won't make it to his 12th -- his 12th birthday. Reporter: Very, very sad. Now, the FBI is helping with the investigation while authorities here are coming under increased pressure to explain why after repeated warnings they failed to stop these horrors and today a suggestion from the government that this was in retaliation for the New Zealand mosque attacks, All right, James, thank you.
This transcript has been automatically generated and may not be 100% accurate.