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A 23-year-old man was in the stairwell of his East Oak Lane apartment building with his girlfriend at about 9 p.m. when a 19-year-old man walked up to them, pistol-whipped the man and shot him in the leg while trying to rob him, according to police.

The victim’s 46-year-old mother heard the commotion from her upstairs apartment, grabbed her legally registered gun, went into the stairwell and shot the suspect, police say.

The 19-year-old robbery suspect died at the scene with one gunshot wound to the chest, according to authorities.

Source: Teresa Masterson for NBCPhiladelphia.