PHILADELPHIA (AP) — Police say a north Philadelphia woman shot and killed a man she said was assaulting and trying to rob her son.

Police say the woman told them her 23-year-old son was entering the East Oak Lane apartment building at about 9 p.m. Tuesday when he was attacked in the stairwell.

Police said the son was pistol-whipped, and a gunshot struck him in the leg.

Investigators say the mother told them she came downstairs with a gun and shot the 19-year-old attacker in the stairwell, where he was pronounced dead.

Chief Inspector Scott Small says the woman has a permit for the weapon and told them she was intervening in a robbery and protecting her son.

No arrests have been made. Her son was taken Einstein Medical Center for treatment.

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