The house where a Brentwood, N.H., man killed a police officer last week exploded because some of the bullets the man fired pierced gas pipes in the basement, and the gas released later came in contact with multiple fires he had set, authorities said today.

Authorities released more details of the harrowing situation faced last Monday afternoon by Officer Steven Arkell, 48, who was killed when he responded to a domestic abuse incident and came under fire from Michael Nolan, 47.

But mystery still surrounded key questions, including Nolan's alleged motive for attacking the officer.

New Hampshire State Police Sergeant Joe Ebert said the one person who might be able to shed light on what led up to the fatal confrontation was unable to: 86-year-old Walter Nolan, who had been in a pitched verbal dispute dispute with Michael Nolan and had let Arkell into the home, moments before Michael Nolan began firing.

Declining to comment on Walter Nolan's mental condition, Ebert said Nolan would know the answers to what went on before Arkell had arrived, but "we are unable to recover those answers."


"We believe he's genuinely unable to recall the details we would like to know," he said.

Ebert said the investigation had revealed that after he was let into the home Arkell was fired upon from "an elevated position within the residence."

He said Michael Nolan's ability to fire from above gave him a "huge tactical advantage" on unsuspecting officers walking through the front door. He said it wasn't clear where Nolan had fired from, but was reasonable to believe it was a cutout window that looked down into the living room.

After Arkell was shot and a second officer, Fremont Police Officer Derek Franek, was forced out of the house by gunfire, which also surprised him from above, the house burst into flames and the fire was punctuated by an explosion.


Authorities said Nolan had set multiple fires in the house, on the first and second floors. Ebert said it was plausible that "he was looking to burn the house down."

But they also said the explosion appeared to be an "unintentional consequence" of Nolan firing bullets that struck a gas line.

Nolan had six guns — three handguns and three rifles — some of which were found in close proximity to his body. He also had a large amount of ammunition, said Ebert.

With one party to the original domestic dispute that brought the officer to the door dead, and the other party unable to remember, Ebert said Michael Nolan's motive for the shooting will remain shrouded in mystery.

"That's something we're simply not going to be able to get the answer to. We're never going to know what he was thinking," he said.