In Britain, there are special squads of armed police officers. So, yeah, if there’s a dangerous situation, the police have to call the police. In 2013, when that soldier in London was rammed by a car and then attacked by two Muslims with meat cleavers, you could see police officers standing back waiting for the armed unit to arrive (meanwhile, two women went to the dying man to try to help and comfort him). The problem with that set up is response time. In the above story, if the guy with the machete starts attacking other people, he can do a lot of damage if the 5-10 minutes it takes the armed officers to arrive.
The cops should carry machetes too.:-)
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A microcosm of the Orlando shooting where the SWAT Team took three hours before going in. That may be OK in a hostage situation but ludicrous in one where there's an active shooter/hacker/whatever.