Investigators say the 18-year-old man, along with a 16-year-old, had robbed two men around 3:45 in the morning.
Police stopped the two suspects on the 300 block of West Penn Street near a Philadelphia housing project in Germantown.
Officers say that's when the 18-year-old raised a sawed-off shotgun and pointed it at an officer.
Officers pulled their guns and fired, hitting the suspect in the chest and legs.
He is in critical condition at Einstein Medical Center.
Officers arrested the 16-year-old and recovered a gun at the scene.
