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.
Pennsylvania State Police spokesman David McGarvey said two of the three people the gunman killed appeared to be neighbors, but gave few further details.
He said investigators "aren't aware of any dispute" between Michael and the victims, who were identified as Kimberly Scott, 58, Kenneth Lynn, 60, and William Rhodes Jr., 38.
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.
(Reporting by James B. Kelleher; Editing by Cynthia Johnston and Paul Simao)