PHILADELPHIA (CBS) –– Police are checking surveillance cameras inside a North Philadelphia corner store for clues after an argument ended in gunfire, Thursday night.

Chopper 3 was overhead 25th Street and Lehigh Avenue, around 11 p.m.

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Police say a group of people were inside a corner take-out store when an argument broke out.

It quickly turned into a fist fight, spilling into the street.

That’s when someone in the fight pulled out a gun and shot the victim in the head.

“There were about eight to seven people inside the store at the time, most of them were young adults, some were male, some were female,” said Philadelphia Police Chief Insp. Scott Small. “You can clearly see them involved in a fight, but we don’t know what the motive was for the fight, at this time.”

The 18-year-old victim remains in critical condition.