It happened around 12 p.m. at the store on Chestnut Avenue and Kings Canyon.
Officers say the man asked a manager to take a look at a rifle locked in the display cabinet, and that he was going to steal it. When the manager tried to stop him, he pulled out another gun, grabbed the rifle, and then ran out of the store.
Witnesses told police they saw a man running in the area with a rifle.
Officers say he ditched the weapons and found him hiding in a nearby bush. The guns were later recovered.
No one was injured in the robbery.