Even if it turns out this man has a diagnoses, was mentally ill at the time what the police were dealing with was a very very serious threat to the public from a man who has already attacked two people
and they had to respond to that threat to keep the public safe
the man may have a mh diagnosis (doesn't mean he was unwell at the time but again he may have been and shall now be diagnosed) but that is not relevant at that point in time the safety of the public is and that is what the police took action on and thankfully no one else was hurt