"Police called to yoga class mistaken for mass killing.* - this really doesn't suggest that the police killed anyone, just that they were called to a Yoga class which someone thought was a mass killing scene. Your suggestion, in fact, sounds weird.
The UK police rarely shoots, and if they shoots it's people with knives or guns. Most of the rare instances where they don't are always a big deal.
And even if people have knives. I've seen videos of UK police dancing around some knife wielder trying to get this done without bloodshed. The Americans think it's silly, but in the end the UK got a lot less people dying unnecessarily, so who is silly on that point?