REVERE — Reyes Bertrand, proud owner of a home on Revere Beach Parkway, knew he had to do something. It was deep in winter, and he was getting complaints from tenants that the building was cold.

Bertrand — Honduran immigrant, father, landlord — descended the stairs that led to the belly of the home he’d bought in 2015, the home that completed his American dream. Long after midnight, he started tinkering with the boiler. Something went terribly wrong.

About 4 a.m. Wednesday, the hot water oil burner ruptured, the resulting explosion sundering walls and filling the basement with steam. Bertrand, who not long ago turned 50, lay dead.

He “loved his house,’’ said Bertrand’s cousin, Fernando Osorio, 40, who was blown from his bed in the basement by the blast. “He was living the American dream.’’

Osorio sustained cuts to his hand and leg in the explosion. He said he didn’t realize his cousin was in the basement until Bertrand’s wife told him.

“I got thrown out against the wall,’’ said Osorio, who grew up in Catacamas, Honduras, with Bertrand. “You couldn’t see anything. Next thing you know, you realize it’s an explosion.’’

Revere Fire Chief Christopher Bright said when firefighters reached the house, at 785 Revere Beach Parkway, they didn’t see smoke or fire, but the boiler had been blown apart with such force that it broke free of its piping and was propelled across the room. They found Bertrand’s body while removing debris, he said.

“He must have been standing right in front of the boiler when it exploded,’’ Bright said. “He got moved to the opposite end of the basement and kind of around the corner.’’

Other people in the house tried to reach Bertrand after the blast, but the smoke overwhelmed them, said Bertrand’s stepson, Walter Lemus.

State and Revere fire officials announced Wednesday evening that “overpressurization’’ caused the explosion, but offered no other details about the malfunction.

During a news conference earlier Wednesday, state Fire Marshal Peter J. Ostroskey said investigators hadn’t been able to pinpoint what caused the burner’s pressurization mechanism to fail.

Bright described the explosion as “a rare occurrence. I haven’t seen one like this.’’

“It doesn’t happen a lot with an oil burner,’’ said Bright, who urged property owners to hire a licensed technician to check their heating systems annually.

Bertrand worked as a manager at Philip R’s Frozen Desserts, and it was there that he had mentioned his boiler trouble to his boss. On Tuesday night, someone came over to help with the equipment, according to Bertrand’s cousin and Bright.

An attorney for the man who visited Bertrand’s home Tuesday night declined to comment.

Revere officials deemed the structure, brick and stone with copper finishing, uninhabitable and instructed the nine people who survived to leave. From outside, a few broken windows in the garage and basement were the only visible damage.

Bertrand had moved his family into the home from an apartment in Everett, upgrading the kitchen and making improvements to the backyard, where relatives recalled spending the summer eating steak and passing time.

“He was always keeping an eye on everything that had to do with the house,’’ said Lemus, the stepson. “He just loved the place.’’

Lemus, 26, said he thought the temperature in the house was fine.

Philip Rotondo, who owns Philip R’s Frozen Desserts in Winchester, said Bertrand’s 10-year-old daughter called him early Wednesday and said her father wouldn’t be coming to work. The company manufactures ice cream truffles and bonbons.

Bertrand also leaves his wife and another daughter, who moved from Honduras with her father’s help, Rotondo said.

“When he started here 18 years ago, I felt like he was my big brother,’’ said Rotondo, who launched a GoFundMe campaign to help Bertrand’s family. “He knew what life was all about.’’

Rotondo said Bertrand talked to him about buying a house and then invited him over a few days after the closing. Becoming a US citizen was another milestone for Bertrand.

“He was so proud of his accomplishment, and I admired him for that,’’ Rotondo said.

Bertrand had recently returned from Honduras, where he visited his parents and spent time in a cabin he built in the mountains, Rotondo said. Bertrand was hoping to bring his parents to the United States this summer for the first time.

Rotondo recalled one of Bertrand’s favorite sayings.

“He said life is too short to be worried,’’ he said. “It’s just unbelievable how this would happen.’’

Laura Crimaldi can be reached at laura.crimaldi@globe.com.