You've been watching too much TV.
I'm no fan of the police (in general), but it appears they were clearly justified in this situation. They even have an eye-witness to back them up.
A club is a deadly weapon, and one blow in the right place can kill a man or render him a vegetable for the rest of his life. Verbally threatening someone with a club and physically moving towards them demonstrates an intent to use that deadly weapon. As such, this was a good shoot. The only mistake they made was letting the guy get that close. He easily could have struck them, even after being shot multiple times, from that close distance.
Just because someone is police officer doesn't mean that they surrender their Right to defend their life with deadly force.
Maybe those bozos at Interior will now rescind the administrative rules against us peasants carrying guns in parks.
I would agree with you if the ranger was solo. He was not. Two rangers should have gotten the job done without killing him.