I am not interested in the nitty gritty of the legality of what the cop did. I don’t think he should have done it, and to me speaks of a lack of training (and the fact that they are reliant on their firearms)
I am aware of the principle of proportional response, and I know the line is generally; if you fear for your life then it is legally acceptable to maim the assailant. But to kill them I think is a step too far.
I do not think the hoe is “reasonably capable of causing “grievous bodily harm””. I think it is reasonably capable of causing injury, sure, such as cuts, lacerations, blunt trauma. I think GBH would be a very unlikely outcome and if confronted with that as a weapon I would not be preparing myself to kill or even maim them. It is a pretty easy weapon to disarm.