Investigators are searching for a possible motive in a shooting spree that left four people dead in rural Pennsylvania, including two apparent neighbors of the gunman, state police said on Saturday.
The violence erupted on Friday when a man with a pistol fatally shot three people in Frankstown Township, about 100 miles east of Pittsburgh, before he was killed in a shootout with state troopers as he tried to flee in a pickup truck, authorities said.
Officials identified the gunman as Jeffrey Lee Michael, 44.
The violence in Pennsylvania unfolded as bells tolled and many Americans observed a moment of silence for the 20 children and six adults shot to death a week earlier by a gunman at an elementary school in Newtown,Connecticut.
The Newtown shooter, 20-year-old Adam Lanza, also shot his mother to death at their home before going on his rampage, which ended with his suicide and has reignited a national debate over gun control.
In the Pennsylvania incident, the gunman in fairly rapid succession shot and killed a woman inside a church, then fatally shot two men at their respective homes - all within a short distance from each other - before trying to flee.
He opened fire at two state police patrol cars rushing to the scene as he passed them on a two-lane road and slammed head-on into a third patrol car. The gunman was killed in an exchange of gunfire with police at the crash scene, police said.
All three troopers involved in the chase were injured - one from the collision, another from bullet fragments and shattered glass, and a third who was shot in the chest but survived thanks to a bullet-proof vest. They were treated and released from a local hospital, McGarvey said.
Police have said that it did not appear that the shooting had any connection to the massacre in Connecticut.