Editor's note: An earlier version of this story said the shooting took place in West Lampeter Township. It took place in West Earl Township.
A man was found in his vehicle with a fatal gunshot wound to his head early Sunday morning in West Earl Township, police said.
Police did not release the name of the man killed.
The Lancaster County District Attorney's Office said the shooter was in police custody as of 12:55 p.m.
The man was "armed and extremely dangerous," authorities said.
Police said the shooting took place just after midnight on Cats Back Road, just south of Ephrata. The man was shot in his vehicle by another motorist.
Police are currently investigating whether the two men knew each other before the shooting.
The suspected shooter drives a black or dark colored Chevy pickup truck, model year 2015 or newer, police said. The truck also has a novelty plate advertising Blaise Alexander Ford and minor damage on the passenger side.
The man was seen at the Sheetz located along Route 322 a few minutes prior to the shooting. He was acting erratically and a had a large dark gun, police said.
The Lancaster County District Attorney's Office is assisting in the investigation.
Anyone with information about the suspect is asked to contact West Earl Township at 717-859-1411.