By Howard Monroe

PHILADELPHIA (CBS) – An overnight shootout left a teenager severely injured. It happened Saturday night on Unruh Avenue in Philadelphia’s Mayfair neighborhood.

Police say two rival groups were shooting at each other just after 8 p.m.

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“At this time we have counted over 65, approaching 70 shell cases on the scene,” Philadelphia Police Inspector D.F. Pace said.

Nearly six dozen shell casing spanning a full block in Mayfair.

“We believe that this gun battle was motivated by a dispute over drug territory in this location,” Pace said.

Police say an 18-year-old was injured in the shooting. He was standing on the corner of Unruh Avenue and Walker Street. That’s when a car pulled up and started firing.

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They say the group he was with returned fire. He was taken in for surgery at Jefferson-Torresdale Hospital.

Several cars were hit with bullets. One car has three bullets in its windshield. A nearby truck also had its windshield shot out and a bullet hole in its side door.

“We know that at least two to three gunmen were involved in this shootout,” Pace said.

One person was arrested. Police also have one of the weapons that was used.

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For a list of gun violence resources in Philadelphia, click here.