WASHINGTON — Investigators in Pennsylvania are looking for the man who they say killed a police officer after a traffic stop Friday night.

Officer Brian Shaw, 25, was shot just after 8 p.m. in New Kensington, about 20 miles northeast of Pittsburgh.

Authorities said the suspect, Rahmael Sal Holt, 29, got out of his car and ran away after Shaw pulled him over. He shot the officer during the chase, New Kensington Police Chief James Klein said at a news conference.

Shaw died at a hospital. He had been with the Police Department for less than a year.

Police have not said why Holt was pulled over, or why he ran away. It also remains unclear how many shots were fired, or whether one of them came from the officer’s gun.

Holt has a lengthy criminal history that stretches to at least 2007.