ROCHESTER, N.Y. — Federal agents are trying to determine the source of 30-round magazines used by William Spengler Jr., a felon accused of killing two western New York firefighters and wounding two others after luring them to his house by setting it ablaze.
Agents are investigating whether the magazines were bought in Pennsylvania, said Scott Heagney of the federal Bureau of Alcohol, Tobacco, Firearms and Explosives. New York state bans the sale of magazines with a capacity of more than 10 rounds, while Pennsylvania has no capacity limit.
‘‘We’re following up on where he got the magazines,’’ Heagney said.
Spengler’s former neighbor, 24-year-old Dawn Nguyen, was charged with buying the convicted felon a semiautomatic rifle and 12-gauge shotgun at an upstate New York Gander Mountain store and lying on the paperwork by saying they were for her. She was not charged with buying 30-round magazines. She has pleaded not guilty.
Spengler, 62, set his home in the town of Webster on fire on Christmas Eve morning, then opened fire on the first firefighters to arrive, authorities said. He killed two firefighters, wounded two others and a police officer, and then fatally shot himself, police said. Beside his body were the rifle, shotgun, a .38-caliber revolver, and a large quantity of ammunition.
A body found in the ashes of the gutted house is believed to be that of his 67-year-old sister, who also lived there. The fire destroyed six other houses in the town on Lake Ontario near Rochester.
Spengler spent 17 years in prison for killing his grandmother with a hammer in 1980.
A rambling three-page letter found beside Spengler’s body detailed how he prepared to destroy his neighborhood and ‘‘do what I like doing best, killing people,’’ State Police have said. But it gave no motive.
High-capacity magazines have been a focus of gun-control debates this year. New York laws enacted this year limited magazine size to seven rounds, later amended to 10 rounds with no more than seven bullets in them.