GUILDERLAND — Coroner’s physician Jeffrey Hubbard told The Enterprise today that he has completed his autopsy report on Alfred E. Watson, who died in a fire at 3825 Carman Rd. on July 17. Watson lived there and operated a tree service from his home. (See related obituary.)

The cause of the fire was smoking in the presence of therapeutic oxygen, Hubbard said; the manner of death was accidental.

Watson had chronic lung disease, the coroner’s physician said. He had oxygen tanks in the house.

Hubbard said that he had heard from Senior Investigator Tom Funk of the Guilderland Police that a witness had said Watson sometimes left the oxygen running and placed the tube over his shoulder, so that he could smoke.

“That’s a bad thing,” said Hubbard.

Asked if oxygen itself can act as an accelerant and cause a fire, Hubbard answered that what happens is everything else “burns better” in the presence of oxygen.

“So if you’ve got a lit cigarette that normally is just a little glowing ash, if you put it in oxygen, it may burst into flame,” he said.

Hubbard said that it did not appear that Watson was injured by the oxygen tank, or possibly several tanks, that are known to have exploded in the house.

Watson did not seem to have died of smoke inhalation either, Hubbard said. There was not much smoke in his lungs, Hubbard said, leading him to believe that he probably died in what is called a “flash fire,” or one that “can kill you quicker than you can absorb carbon monoxide.”

Normally a flash fire is very hot and paralyzes breathing by hot gases going down the throat. That is the usual explanation, he said, that they look at when a fire victim has not absorbed significant smoke.

The police had not yet definitively identified Watson as the victim until now, but the family had been sure all along.

“They say there’s someone in there,” said a distraught family member watching on July 17 as firefighters worked to contain the blaze at 3825 Carman Rd.

“If the dogs were in there, he was in there,” she said, looking at the home’s burned-out front window. “A neighbor heard them barking in the window,” she continued. “He never went anywhere without those dogs.”

The family held a memorial service for him at New Comer Cannon Funeral Home on July 25.

William Dvorscak of the Guilderland Police — who is heading the department’s team that supports State Fire in its investigation — said that the team had looked for two dogs on the first floor. The body of one dog was located, he said. He did not know if the second had ever been found. A third dog was found dead, he said, on the second floor. The brick house contained a total of three apartments.

Neither dental-record comparison nor DNA testing was used in this case, Hubbard said. “We only do that if it’s a body found out in the woods or something, not when it’s somebody found in his car or in his house. Here he’s in his house, he’s the right sex, he’s the right size. We used the I.D. made by law enforcement at the scene.”

There was a large fire at the same address in May 2014, Guilderland Police Captain Daniel McNally confirmed, but it was completely unrelated to this one, he said. McNally heads the department’s fire investigation team.

The earlier fire was caused by careless cooking — someone tried to use a towel to put out a flaming pan of oil — and involved a tenant who no longer lives there, McNally said.

The investigation into the recent fire was led by State Fire, he said.

The home belonged to Watson’s mother and stepfather. There were also two apartments in the building. No other occupants were hurt, although the house was, said Guilderland Fire Department Chief Scott Jill, a total loss.

Hubbard, the coroner’s physician concluded, “They tell you when they put the oxygen tank in your home not to smoke, but the reason he needed the oxygen was because he wanted to smoke. This isn’t the first, or the second, or the third of these I’ve seen.”