The gun was found Thursday near where the suspect in the shooting, Sergei Pomazun, was arrested, and has been sent to experts for examinations, Yelena Kozyreva, an aide to the head of the investigative department of the Russian Investigative Committee, told ITAR-Tass.
On Monday, Pomazun allegedly entered a hunting store and opened fire. He then exited the store and allegedly continued shooting. He fled the scene in a vehicle.
Six people were killed in the incident.
Police arrested Pomazun Tuesday night near a railway station. He allegedly attacked the arresting officers, seriously wounding one of them.