A gun was recovered by officers who were breaking up a fight Friday at the Smith Haven Mall.
Police say 18-year-old Tavion Elting, of East Patchogue, has been charged with criminal possession of a weapon.
Last week, a 16-year-old male was stabbed outside the mall's food court.
Some shoppers told News 12 that they are concerned about their safety.
"It makes me uneasy to know that something like that happened inside my local mall," explained a shopper.
Authorities urge shoppers to be aware of their surroundings. They say never leave valuables in cars and avoid carrying large amounts of cash.
Suffolk and Nassau police say they are stepping up patrols at shopping centers during the holiday season.