It appears someone forced their way into the vehicle, which was locked and parked in the garage of a residential complex in Malden, just north of Boston, and took the patrol rifle from its secured mount, spokesperson David Procopio said.
A service rifle was reported stolen Thursday from a Massachusetts State Police vehicle.
"At this time we have no indication of the rifle being used subsequent to its theft," he said in an emailed statement.
JAN. 6 PROTESTOR WHO USED STOLEN BATON, STROBE LIGHT AGAINST CAPITOL POLICE GETS 4 YEARS
It is standard department procedure for troopers who are assigned rifles to secure them in their cruisers while off duty. No other information was disclosed.
Broadcast video from the scene showed the cruiser, a Ford SUV which appeared to have a broken door lock, being towed away.