ALBANY, N.Y. (AP) — William Spengler raised no alarms in prison for 17 years and for more than a decade afterward. Well-spoken, well-behaved and intelligent, his demeanor was praised by four straight parole boards that nevertheless denied him parole, worried that bludgeoning his 92-year-old grandmother with a hammer showed a violent streak that could explode again.

After his sentence was up in 1996, he stayed out of trouble until 2010, police said Friday. That’s when Spengler went to a sporting goods store with a neighbor’s daughter, picked out a Bushmaster semiautomatic rifle and a shotgun and had her buy the guns that the convicted felon couldn’t legally possess. On Monday, he used the weapons to ambush firefighters lured to a blaze he set at his house in upstate Webster, killing two people and wounding three others before killing himself.