Reading the article, this guy seemed to be a veteran officer, which usually means you've been in a number of fights. I'm sure he first tried to calm the guy down but after that it went downhill. The article says the naked guy was muscular so I believe he's probably doped up. This is a bad combination for a policeman, deranged, drugged and strong.
I was wondering if he had any backup. I've been in a number of battles with people much bigger than me, and drugged up too. Like I say, I just thank God I keep practing my martial arts. Sometimes you don't have time to get to pepper spray, your gun or anything else. It gets pretty hairy when someone tries to take your gun.