Police have not yet said if Shaw discharged his weapon.
Pennsylvania state police have issued an arrest warrant for 29-year-old Rahmael Sal Holt. Authorities urge anyone with information to call 911.
"We were able to find and seize the vehicle that we believe to be involved in this incident", New Kensington Police Chief James Klein said.
A $43,500 reward is being offered for information leading to Holt's arrest.
Shaw, 25, was pronounced dead at Allegheny Valley Hospital after he was shot in the midst of a foot chase when he pulled over an SUV on a road in New Kensington around 8 p.m. on Friday.
Limani would not discuss other details of the case, including the reason for the traffic stop, saying it could compromise the ongoing investigation. "We ask all Pennsylvanians to join us in keeping Officer Shaw's family and fellow officers in their thoughts". It also remains unclear how many shots were fired, or whether one of them came from the officer's gun.
Police have recovered a brown, older model Jeep Grand Cherokee wanted in connection with the shooting.
Holt was charged by authorities with first-degree murder and murder of a police officer.
Officer Shaw was killed while on duty on November 17th.
One tribute honored the fallen officer with a moment of silence at Saturday night's National Hockey league (NHL) game between the Pittsburgh Penguins and Chicago Blackhawks.
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