(CNN) -- A Massachusetts police dog searching for a handgun not only found the weapon but fired it with his paw, a police chief said Sunday.
No one was injured when K-9 search dog Ivan discharged a bullet as he indicated the gun's location, Lawrence Police Chief John Romero told CNN.
"Everyone on the scene was startled, including Ivan," Romero said with a chuckle.
The search for the weapon began after a police officer on patrol early Saturday morning was responding to hearing three gunshots, according to Romero. The officer followed a vehicle, which sped off. A short time later, a passenger in the rear seat exited the vehicle and ran to a nearby snow bank to bury something.
The passenger re-entered the vehicle, and the officer stopped it but waited for backup before ordering the three men out of the vehicle, Romero said.
After the men exited the vehicle, Ivan's handler, Essex County Sheriff's Lt. John Pickles, commanded the dog to search for a gun after a shell casing was found in the backseat of the car, Romero said.
Ivan is trained "to paw" if he finds something.
"I surmise that the snow was there for a week, and it was probably like ice," Romero said. "The individual probably was not able to bury it very deep, and he had no time."
After Ivan recovered and fired the weapon, the three men were arrested and charged with possession of a firearm, possession of ammunition, receiving a firearm with a defaced serial number and receiving stolen property, Romero said. The individual believed to have buried the gun was also charged with discharging a firearm within 150 feet of a highway and carrying a firearm without a license. The semiautomatic Ruger was stolen from New Hampshire in October 2012.
As of Sunday, all three were being held in jail and awaiting a Monday arraignment, Romero said.
CNN's Rob Frehse contributed to this report.