Transcript for At least four Americans killed in Sri Lanka Easter bombings
Every parent thinks that their son is the best. Reporter: Curious and confident. 11-year-old Kieran was such a good student he was about to skip sixth grade. Kieran was articulate, insightful. He wanted to work on diseases like Alzheimer's disease. Reporter: But now he'll never walk through the doors of his Washington, D.C. School again. The terrorists didn't know who they were killing. We should know what the world lost, what they took from the world. A brilliant mind who was going to be a neuroscientist and now he won't make it to his 12th -- his 12th birthday. Reporter: Kieran shafritz de zoysa was one of nearly 300 killed and at least 500 wounded in coordinated bombings in Sri Lanka on Easter Sunday. The island nation coming to terms it one of the worst acts of terror since 9/11. And today more chaos as police continued to find and defuse more bombs. A huge explosion just went off just around that corner there. A huge scream went up from the crowd over there. You can see them running toward our position here where we are now. It was a police detonation but that was absolutely terrifying. Reporter: Everyone on edge as we learn officials were warned at least three times of possible terror attacks. Many asking why authorities failed to prevent the mass carnage and what they could have done. It started on the morning of Easter Sunday. One of the holiest days in christianity. Colombo, Sri Lanka's capital, the first to be hit. We are right outside St. Anthony's church where one of the suicide attackers struck. Time here forced still at 8:45 A.M. When the first suicide bomber unleashed destruction through the wooden pews as worshippers gathered in prayer. The bomb went off and you ran inside the church. Yeah. Reporter: This neighbor rushed into the church as soon as he heard the explosion. He told me it was covered in blood and filled with the dead and injured who he brought to the hospital. At the same time about an hour north of the capital a second suicide blast, where the faithful once knelt only glass and debris. A celebration of new life now ravaged by death. Minutes later a third explosion shattering a holiday brunch at the shangri-la, a favorite among foreign tourists. Even from the 25th floor the impact was very loud and my wife and I just wrapped up our things and decided to evacuate. Reporter: Then around 9:00 A.M. Almost simultaneous blasts at three other locations. A church on the country's eastern coast and two hotels in the capital. Alex arrow had been trying to reach his only child Kieran at one of them, the cinnamon grand hotel. Couldn't pick up the phone, and he texted me back "Can't talk right now." Because he was in the elevator going to breakfast. Reporter: Kieran was in Sri Lanka visiting his mother on that fateful morning. He got a shrapnel wound that pierced his heart. It could have been a foot or two in either direction and it would have been totally different. He bled out in the restaurant. There's not a damn thing I can do for him in Sri Lanka. Reporter: And even then the terror wasn't over. Hours later two more explosions, one at a hotel just south of Colombo and a final one in the suburbs of the capital when a suspect being questioned by police detonated a suicide bomb. Eight explosions in total. An overwhelming number of deaths. Within hours Sri Lankan security services apprehended at least 24 suspects and a murky picture began to emerge of who authorities say are behind these attacks. Sri Lankan TV showing security footage being investigated by police that purports to show one of the suicide bombers at St. Bastion church in agumbo. Local officials say he may have been part of a little known group the nationalal thawahid jaman. They are exclusive to Sri Lanka. They are considered a domestic terrorism group. It's the first time authorities say this organization has pulled off such a large-scale attack, leading officials to believe they may have had some help. The multi locations, the fact they used explosive devices that all went off, it's very possible that this terror group is connected to a larger terror group that has that sophistication. We don't see that only a small organization in this country can do all that. That is all we have now investigating about the international support for them. Reporter: But many pointing out that there were ample signs leading up to the Easter massacre. There was a warning that was issued by a police chief about ten days before the attack. And it's a question of whether that warning was taken seriously by all of the law enforcement agencies and the government throughout Sri Lanka. Reporter:his advisory was sent by a Sri Lankan police official on April 11th, specifically warning of suicide attacks targeting churches by national thawahid jaman. According to the "New York Times," a senior adviser to the country's president has denied any security lapses. Everyone has done their jobs. These kinds of alerts are coming from time to time." Some now pointing their fingers at the president and the country's prime minister saying political rivalry between them led to a breakdown in communications. Sri Lanka is no stranger to warring factions and political turmoil. The majority of Sri Lanka's population are sinhalese and buddhist with less than 10% Christian. For decades the Sri Lankan army fought a brutal war against the tamil tigers a militant organization credited for some of the earliest uses of suicide vests in the 1980s. The tamil tigers used it as a weapon of choice. They killed hundreds, tens of thousands of their adversaadversaries, civilians and military. Reporter: Their civil war ended ten years ago when the army defeated the tamil tigers. Even though the war is over there is this type of violence and inciting of violent rhetoric that has occurred within Sri Lanka. So it hasn't ended. The civil war is over, but the activity has not stopped. Reporter: But an attack of this scale is unprecedented. The number of victims and wounded horrifyingly high. Among them at least four Americans. Like dieter Kowalski from Denver. He worked for the education company Pearson and had just arrived at his hotel when the bomb debt nailted. And Kieran shafritz de zoysa, that young boy who aspired to be a neuroscientist. When this news passes, there won't be attention on this particular incident anymore and it will be on to the next thing. But Kieran was -- the world has lost a great mind, and that's why we're doing this interview.
This transcript has been automatically generated and may not be 100% accurate.