Most UK police do not carry guns, yet those police forces still have firearms officers, and in a case like this where they would be responding to a suspected armed murderer and hostage taker, you can bet that firearms officers would be involved. Those police forces have substantial armories, they just don't issue a firearm to the majority of cops. Comparing UK firearms officers to US cops, I would contend that armed officers in the UK are less likely to kill because of the cultural and structural unacceptance of such killings in their country.