PHILADELPHIA (CBS) — Police are working to identify a suspect and a motive after a teenager was shot and killed overnight in South Philadelphia.

Police responded to the 2300 block of South Marshall Street just after 11 p.m. Monday.

Authorities say an 18-year-old man was shot in the back, and then managed to run inside a nearby home for help.

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He was rushed to the hospital but died a short time later.

“They found multiple shell casings on the 2300 block of South Marshall. They also found a shell casing in a car that was shot up in the 600 block of West Fitzgerald,” said Philadelphia Police Captain George Fuchs.

Police say, two eyewitnesses, including the victim’s brother, are being interviewed by homicide detectives.