Transcript for Death toll in Sri Lanka terror attack rises to at least 310
We begin with the death toll rising in Sri Lanka following the coordinated bombings on Easter Sunday dozens of members of a local terror group are under arrest in connection with the explosions. Authorities believe the suspects were aided by an international network. At least 310. People are now dead with hundreds of other victims. Among those victims killed at least four Americans including an eleven year old boy from Washington DC. Overnight vigil straps all the way back to the US as we learn more about the investigation into the attacks. A second wave of chaos in Sri Lanka. A van full of explosives discovered in the capital city just. One day after a series of coordinated attacks left more than 300 people dead. Huge explosion just went off just around not cornerback ABC seeing Longley and was just yards away when the bombs went off buildings around hang. When guys shot since cheers criminal from the crowd and that. You can see them running toward the position of Elian now police on high that we don't know what to walls with a nod to the police destination that was. But this search is part of the massive investigation. Into the deadly Easter Sunday bombings. Dozens of Sri Lankan nationals already arrested but officials now say they are certain the culprits had help from outside the country. Police are viewing these security videos broadcast on tree launching TV. This man purportedly one of the bombers seen maneuvering the crowd while another wrinkle shows him walking by worshippers at the saint Sebastian church. Minutes later the group of that church was blown completely off. Among the dead are four Americans including forty year old Dieter Kowalski who traveled from Colorado to Sri Lanka. For business and eleven year old cure in shock free to do is always who was killed while waiting for breakfast won't make it's it. His twelfth. His twelfth birthday here and was about to start seventh grade and wanted to be a neuroscientist. They have no idea. Favorite thing just blew himself up and have no idea. No I did. This story should be told the FBI is now assisting Sri Lankan authorities in the investigation. As reports lake officials. Cleaning they ignored warnings about an imminent attack. And we're now learning that a memo was sent to local authorities with the omelet ominous title information. Of an alleged planned attack many are now asking whether that threat was taken seriously.
This transcript has been automatically generated and may not be 100% accurate.