PHILADELPHIA (CBS) – Police are searching for a robbery suspect who exchanged gunfire with an officer in the parking lot of a Northeast Philadelphia convenience store.

Investigators say Joseph M. Brock, of Philadelphia, robbed a 7-Eleven at Welsh Road and Bustleton Avenue at about 2 a.m. Sunday.

Police say the 20-year-old Brock then exchanged gunfire with an officer who was called to the scene for the initial robbery.

Authorities say Brock fled, but police found the gun he used. They are trying to determine whether the robbery was related to several other recent gunpoint robberies in the area.

No one was hurt during the incident.

Police say Brock has a previous criminal record that includes DUI, arson, burglary and theft.

Brock is a white male, 5’9″, 130 lbs. with brown hair and grey eyes. He was last seen wearing a black hooded sweatshirt with the number 77 embroidered on left side/front.

Anyone with information on his whereabouts is urged to contact police.