A fifth-grade student from Washington, D.C., was among the victims of the deadly Easter Sunday bombings in Sri Lanka that killed at least 321 people and injured 375 others.

Kieran Shafritz de Zoysa, who would have turned 12 in August, was on a leave of absence from Sidwell Friends School to study and live in Sri Lanka, where his mother is originally from.

Sidwell Friends School boasts notable alumni including Chelsea Clinton and Malia and Sasha Obama.

Kieran's father, Alexander Arrow, told NBC News that his son was having breakfast at the Cinnamon Grand Hotel in Colombo when a suicide bomber entered and detonated his backpack.

The boy's mother and grandmother both survived. According to UNICEF, at least 45 children were killed in the attacks.

"Kieran was just a foot in the wrong direction," Arrow said, adding that they had exchanged text messages less than an hour before Sunday's blast.

Arrow said Kieran was hit by three pieces of shrapnel, one of which went into his heart. By the time he got to the hospital, he did not have a pulse.

"I keep going over the last 11 and a half years and thinking about all of the little memories that we have together," Arrow added, describing his son as "articulate and insightful and kind."

Speaking from Nevada, Arrow said Kieran dreamed of becoming a neuroscientist. "He wanted to address Alzheimer's or other great unsolved neurological diseases and I know that he would have done that."

Kieran was completing his final semester at a Sri Lankan school and was looking forward to returning to Washington when the blasts happened.

"He's never gonna be a teenager," Arrow said. "The terrorists had no idea who they were killing ... who they happened to hit was an incredible person who was going to do great things."

The near-simultaneous bombings occurred during church services and Easter brunch at hotels. The attacks were carried out by seven suicide bombers, and 24 suspects have been arrested, authorities said Monday.

Two teenage siblings who were U.S.-U.K. dual nationals were also among those killed.

Amelie Linsey, 15, and Daniel Linsey, who both lived in London, were killed while eating breakfast at the Shangri-La Hotel on what was the final day of a family vacation.

Their father, Matthew Wells, told The Times of London how he attempted to save his son's life. "My son looked worse than my daughter," he was quoted as saying. "I tried to revive him. A lady said she’d take my daughter."

He added: "I carried my son downstairs to an ambulance, we took him to the hospital. I yelled, ‘Please help my son, please help, please help.’ I thought my daughter was better off. I couldn’t find her because I was with my son. They sadly passed away.”

Wells, 60, was reportedly born in the United States but is now a London-based financier.

Dieter Kowalski, 40, a Denver man on a work trip staying at the Cinnamon Grand was confirmed Monday as another of the Americans who died in the explosions.

The State Department said that several U.S. citizens were also seriously injured by the blasts.

Sri Lanka's Foreign Ministry said Monday that 31 foreign nationals were killed. Fourteen others remained unaccounted for.

Meanwhile, famous Sri Lankan TV chef Shantha Mayadunne and her daughter, Nisanga, were identified as being among the victims.

They were having breakfast with family members at the Shangri-La Hotel, with Nisanga posting a photo of the Easter Sunday gathering on Facebook not long before the explosion.

The fate of the other people who appeared in Nisanga’s photo remained unclear Tuesday.