(Reuters) - A fifth-grade student at an exclusive private school in Washington, D.C., and a Denver man on a business trip were among the U.S. residents killed in the Sri Lanka Easter attacks, a media report and the man’s employer said on Monday.

Suspected suicide bombers set off explosions in at least seven churches and hotels in the capital Colombo on Easter Sunday, killing 290 people and wounding nearly 500.

At least four U.S. citizens were killed and several were seriously injured in the attacks, a U.S. State Department spokeswoman said.

Kieran Shafritz de Zoysa, a fifth-grader at Sidwell Friends, died in one of the blasts, the school emailed to friends and family, according to WJLA television in Washington.

Kieran was living in Sri Lanka, on leave from the school and expected to return, the email said. Fifth-graders are around 10 years old.

“Passionate about learning, he adored his friends, and was incredibly excited about returning to Sidwell Friends in the coming school year,” school principal Mamadou Gueye wrote in the email.

The boy’s citizenship was unknown. Staff at the school did not respond to requests for confirmation.

President Barack Obama’s daughters, Sasha and Malia, and Chelsea Clinton, daughter of President Bill Clinton, all attended Sidwell Friends.

Dieter Kowalski, a Wisconsin native who lived in Denver, was also among the victims. He was on a business trip for the British education publishing company Pearson, which has 800 employees in Sri Lanka.

“Dieter had just arrived at his hotel, where many of our colleagues have stayed over the years, when he was killed in an explosion,” Pearson Chief Executive John Fallon said on LinkedIn.

All other Pearson employees in Sri Lanka have been accounted for, Scott Overland, a company spokesman, wrote in an email.

A senior leader on a technical services team, Kowalksi was on assignment to work with local Pearson engineering teams, Fallon said.”Colleagues who knew Dieter well talk about how much fun he was to be around, how big-hearted and full-spirited he was. They tell of a man to whom we could give our ugliest and most challenging of engineering problems, knowing full well that he would jump straight in and help us figure it out,” Fallon said.

Kowalski himself appeared enthusiastic about his trip in his final Facebook post on Friday: “And the fun begins. Love these work trips. 24 hours of flying. See you soon Sri Lanka!”