One woman is dead and a home burnt beyond repair after a fire on Forss Avenue Thursday morning.

The home is owned by Carl and Lisa Thompson, according to borough assessment records. Petrina Calvin, who lived in the home with her husband, Brian, escaped from the house with her 2-year-old child. The downstairs renters, and the woman who died in that apartment, were not identified.

The cause of the fire is not yet known. More details should be available pending an investigation by the state fire marshal.

Dozens of friends, family and neighbors watched from the street as members of South Tongass Volunteer Fire Department battled the blaze throughout the morning. By the time the fire was put out by noon, all that remained was the smoldering frame of the house and the stone mantle of a fireplace.

South Tongass Volunteer Fire Department Chief Steve Rydeen says the 911 call came in around 9 a.m. When firefighters arrived on scene, the house was already engulfed. A boat, truck and detached garage also were damaged.

But it was some time after emergency responders arrived, Rydeen says, that they learned about the woman still inside.

“It was probably 15 minutes into the incident that I found out there was a a possible person unaccounted for,” says Rydeen. “At that time we assessed that the building was not stable enough to send anyone in. We eventually found a person, deceased, in the back corner bedroom of the lower unit.”

The Calvins declined to speak on the record for this story. Firefighters on the scene said they had no information about the dead woman, and will not release information until the state fire marshal completes its investigation.

Firefighters prevented anyone on the scene from getting close to the smoldering remains of the house, due to fears of imminent collapse.

Chief Rydeen confirmed that one large explosion accompanied the fire, but could not say whether it was caused by one of two known propane tanks in the home.

The chief did say that Brian Calvin owned a number of firearms; the ammunition for those guns, he says, exploded during the fire.

The sound of those explosions, neighbors say, was distinctive.

Harold Carson lives directly across the street from the Calvins.

“I entertained the thought of going up the driveway and pulling the boat down, but then the bullets started going off,” says Carson. “There were literally bullets ricocheting off the windows of the house next to it.”

Another neighbor, Kendra Vonda, lives directly next door to the Calvins. She says that she was at home with her baby when the fire started, and was not aware of it until neighbors and firefighters came running to her door.

“It was really, really scary to see that. I had my little baby with me, she’s 10 months old,” says Vonda. “That house is just toasted. I guess a lady died in there? That’s so sad. The people next door, I mean, they saved our lives. We wouldn’t be here if it weren’t for them.”

A couple of donation sites have been set up to aid the Calvins, who friends say have lost everything.

Alltek Network Solutions at 2300 Tongass Avenue is accepting donations of anything, from gift cards to clothing, during regular business hours.

And the South Tongass Alliance Church, which the Calvins attend, is accepting checks made out to the church with “Calvin” on the memo line. The church office — at 540 Water Street, Suite 303 — is open 9 a.m. to 4 p.m. Tuesdays through Fridays.