BANGOR – A fire that killed one man, injured another and destroyed a Bangor apartment building Thursday was started accidentally by someone in the first-floor apartment, officials said Friday.

Meanwhile the first-floor tenant who was burned as he tried to rescue a visiting friend from the burning building was discharged from Eastern Maine Medical Center.

Robert Beale, 31, lived in the first-floor apartment of the three-unit apartment building. He was injured when he tried to re-enter the building to save his friend, 30-year-old Stephen Chase of Bangor, who was visiting.

Firefighters found Chase’s body inside a walk-in closet.

Two tenants of the other apartments escaped the fire uninjured.

On Friday, what was left of the home was being boarded up. The building, owned by Robert Cort of Hampden, is considered a total loss.

Public Safety Spokesman Stephen McCausland said Chase and Beale had been out at an area nightclub and were awake when the fire broke out. McCausland said it appeared the fire started either near or on the bed, but it remained unclear exactly how it began.

“Beale was a smoker, but we don’t know that that was the cause,” he said.

The apartment consisted of only two rooms, McCausland said, a kitchen and a combination living room and bedroom.

McCausland said the fire burned so hot and fast that exact details of how the fire began remained under investigation.

The fire was reported at 4:37 a.m. Thursday by the upstairs tenant. When firefighters arrived, flames were shooting out the front and back windows and had crawled into the walls and up into the roofline.

Efforts to ventilate the fire were hampered by the large number of utility lines in the area, fire officials said.