A Pennsylvania man was arrested on first-degree murder and other charges Sunday in the "savage" road-rage shooting of an 18-year-old woman last week, authorities said.

David Desper, 28, of Trainer, turned himself into authorities in Chester County outside Philadelphia, District Attorney Tom Hogan said. Desper and Bianca Roberson, who just graduated from high school, were trying to merge into a single lane Wednesday, Hogan said.

"They jockeyed for position, and he wasn't happy, so he pulled out a gun and shot Bianca in the head, killing her instantly," he said.

Roberson's car veered off the road and crashed into a tree while the shooter fled in a bright red pickup. Surveillance video and tips from the public helped identify the car, and authorities urged Desper to turn himself in.

Hours after he did, the truck was found with a semiautomatic handgun inside that police say was used in the shooting.

Desper is white and Roberson black, but Hogan declined to link the shooting to race.

"This appears to be a savage, senseless and brutal act from one human being to another human being," he said.

Contributing: Associated Press