A Denver man on a work trip to Sri Lanka was confirmed Monday as one of four Americans killed in a series of deadly bombings that shook the island nation on Easter Sunday.

Dieter Kowalski, 40, was staying at the Cinnamon Grand, one of the three hotels and three churches hit by the explosions that killed at least 290 people and injured 500 more.

Dieter Kowalski. Facebook

Originally from Wisconsin, Kowalski posted on Facebook on Friday that he was flying to Colombo, Sri Lanka.

“And the fun begins," he wrote. "Love these work trips. 24 hours of flying. See you soon Sri Lanka!”

Kowalski's LinkedIn page listed him as a senior technical operations lead for Pearson, an education publishing and assessment firm.

The company confirmed his death in a statement Monday.

"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 CEO John Fallon wrote in a note to employees.

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Fallon added: “Colleagues who knew Dieter well talk about how much fun he was to be around, how big-hearted and full-spirited he was. ... In these desperately difficult days, let’s honor Dieter by showing that love ourselves, by taking extra care of each other — at work, at home and in our communities."

The six almost simultaneous blasts took place Sunday at the Cinnamon Grand, Shangri-La and Kingsbury hotels in Colombo, as well as three churches. Police later reported two more explosions.

The bombings occurred during church services or while Easter brunch was being served at the hotels. The blasts collapsed ceilings and blew out windows.

The attacks were carried out by seven suicide bombers and 24 suspects had been arrested, authorities said.

Sri Lanka's government said the bodies of at least 27 foreigners had been recovered. A State Department official confirmed Monday that at least four of the dead were American citizens.

Also killed was Kieran Shafritz de Zoysa, who was a fifth-grader at the Sidwell Friends School in Washington, D.C., NBC Washington reported. He was studying in the country and was supposed to have returned to Sidwell; his nationality was not immediately clear.

Staff at a hospital in Colombo told NBC News that they treated an American woman identified as Chimai Tran-Luu, adding that she was later discharged.

Three children of the Danish billionaire Anders Holch Povlsen, who owns the clothing company Bestseller and is a shareholder in online retailer ASOS, were among those killed in the attack, a company spokesman confirmed to NBC News.

St. Anthony's Shrine in Colombo, Sri Lanka, was among the sites targeted. Eranga Jayawardena / AP

On Monday, Sri Lankan authorities said that they had been warned about a terrorist plot targeting churches and tourist destinations weeks ago.

"We never expected it to be so big," Hemasiri Fernando, the chief of staff to Sri Lanka's president, told NBC News. "We never thought it would happen so soon."