A security guard at a 7-Eleven store in Silver Spring, Maryland, shot and killed a man after a dispute turned physical, Montgomery County police say.

Deon Christopher McDonald, 27, of Hyattsville, went inside the store on Georgia Avenue just before 4 a.m. Sunday to purchase an item, police say.

McDonald got into an argument with the store clerk during the transaction, and the on-duty security guard intervened, according to police.

The dispute between McDonald and the security guard continued outside, and at some point, it turned physical. Police say the 44-year-old security guard then fire his weapon, hitting McDonald.

McDonald died at the scene.

Police have not identified the security guard and have not said whether he will be charged. The security guard is employed bya company that is contracted by the property manager, police said.

Anyone with information that can help police is asked to call 240-773-5070.