Police are investigating the overnight shooting death of a teenager in South Philadelphia.

The 18-year-old man was shot in his back and chest on the 2300 block of South Marshall Street at about 11:20 p.m. Monday, Philadelphia police said.

He was taken to Thomas Jefferson University Hospital, where he died at 1:05 a.m. Tuesday. The victim’s name has not been released.

Capt. George Fuchs told reporters at the scene that investigators found numerous shell casings in the area and blood inside a property where the victim ran after he was shot.

The motive for the killing remained unknown Tuesday morning.

No arrests have been made, and no descriptions of any suspects were available.