A Philadelphia police officer was shot in the neck and James Caldwellwas in critical condition Saturday night, officials said.

The 31-year-old officer was in critical condition and undergoing surgery at Temple University Hospital, Police Commissioner Kevin Bethel said during a news conference outside the hospital.

The officer, a veteran of more than six years on the force, and his partner stopped a car with four people inside shortly before 8 p.m. The officers saw a person with a gun holster and the suspect fled, firing three times at the officers, Bethel said.

The wounded officer’s partner returned fire, but it was not immediately clear if the officer who was shot fired his weapon.

The shooting suspect and all the people who were in the car are in custody and are considered “persons of interest” at this time, Bethel said.

Philadelphia Mayor Cherelle Parker asked residents to pray for the officer, whose name was not released.

“He didn’t expect that he would be in a fight for his life,” Parker said.