Three bandits stormed into a Brooklyn jewelry store with guns blazing yesterday, making off with gems, police said.

The trio — one of them packing a gun — entered Benz Jewelers on 86th Street in Bensonhurst at about 1 p.m.

The gunman fired a single shot into the wall and announced a stickup. The robbers then forced the unarmed owner to the ground, and then looted the jewelry cases.

Cops are investigating whether a 17-year-old man found later with a gunshot wound to his stomach at a nearby school had any connection.

The teen was taken to Lutheran Hospital where he was in stable condition.

It was not clear how much was taken.