The standing orders are to lock the doors after hours. Further, most federal locations have a policy to close the location i.e. lockdown when there is a riot.
Someone had to order the police to let them in. Who?
If there are two officers with loaded six-shot revolvers and 500 angry people storm in, it is best for the officers to smile.
There are reasons why many of you don’t want to be limited to 10-shot magazines.