How can they claim that the man "was behaving strangely"? It was just a naked man into a fountain in the town center near the city hall with a 20 cm. knife screaming „Ich bin der Messias!“, advancing on a police officer and obviously threatening him to death... there's nothing wrong with it, mmmkay?
The cop not only acted appropriately, but he had no options left, three patrols tried to stop him in some dozens of different ways with no luck, what was he supposed to do, to wait to get stabbed before reacting?
In Europe, they always favor criminals over law enforcement. I dont know why anyone would want to be a cop over there.