NORRISTOWN, Pa. (AP) — Authorities say they are investigating the shooting deaths of two teenagers following an alleged robbery attempt in southeastern Pennsylvania.

The Montgomery County district attorney and Norristown police said the shooting occurred in an alley in Norristown at about 8 p.m. Friday night.

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Police and prosecutors said their initial investigation indicated that the shooter was walking to his car from home when two teenagers pulled a gun on him and tried to rob him.

Authorities said there was apparently a struggle over the gun held by one of the youths, and the shooter “used his legally registered gun to fatally shoot both of them.” He then rendered aid and called 911.

Authorities said one youth was shot five times and the other was shot once in the torso and once in the finger Both shooting deaths were classified as homicides. Authorities said police found a “ghost gun” with an extended 30-round magazine at the scene.

The names of the two youths killed weren’t released because of their ages, but officials said both were 17 and from Norristown. The man who shot them was questioned and released. District Attorney Kevin Steele said no charges were immediately filed, adding that “We have a lot of work to do on this investigation.”