When I first saw this story elsewhere, the locked racks weren’t mentioned. This story mentions them and pretty much confirms what I figured – that the weapons stolen were most likely shotguns.

WBAL.com

Howard County police say two marked police vehicles were broken into overnight in Elkridge. In one case, a secured police-issued firearm was stolen.

Both cars were parked separately in a residential Mayfield community. Other police property was also taken, including ammunition, blank police forms and a police baseball cap.

[...]

In both cases, which police think are linked, the suspect broke a window on the car and forcefully removed the property. Police say the gun was properly secured in a locked rack affixed to the interior of the car. The suspect stole ammunition from the other car.

The police department has issued a temporary prohibition on storing firearms in police vehicles even when they are properly locked and secured.

Officers are now required to bring their weapons indoors to be stored, using trigger locks and gun lockers.

Anyone with information is asked to call police at 410-313-3200. The department is offering up to a $2,500 reward for anyone who can provide helpful information, Llewellyn said.