American police are, for the most part, trained to respond to an active shooter scenario with a patrol rifle. Hell, I've seen chicago police responding to gang shootings with AR15s. These are regular beat cops too, not SWAT officers. Almost any situation where an individual may be wearing body armor, whether it be an active shooter or a home invasion, the police responding will probably be armed with more than a handgun. This has not always been the case, though. This shift has largely occured in the last decade or so.
Are things that bad already? In Europe we almost never see police with rifles. (nor criminals with body armor either)
What do they use as patrol rifles?