But the police officer is usually INSIDE the car where the gun is stored. He doesn't have to leave a building (possibly under fire), get his rifle, and then run back -- all while people are being killed.
Police officers park their cars all the time around here. They absolutely are not always in the car. I see police officers inside of malls for example, and they aren't carrying rifles.
It's pretty simple...a rifle in the car in the parking lot or otherwise right nearby beats a rifle in a car (with an office also in the car) many miles away.
Still in a perfect world if it were up to me there would be storage inside the building at a need to know basis location. And there would be multiple such locations. All rifles would be configured the same or substantially similar