In such situations it's possible to bring in special police units with guns; that doesn't mean you now have to equip every bobby with one. Thankfully in the UK regular police still don't carry a gun (except for NI, but that's historical), and, unsurprisingly, the number of people killed by police in orders of magnitude lower than the US. And the UK homicide rate is 4 times lower than the US, which proves that having more cops with guns does _not_ reduce violent crime.