I have to agree. When in packs, they go into kill-mode. They feed off each other's blood lust. They lose control.
That is plainly true for the most part. But in this specific example I wasn't able to see whether every one of the cops present had struck or kicked the subdued prisoner. One thing is certain, the Internal Affairs investigators will focus on finding at least one of those cops who will insist he didn't participate in the beating and they will pressure him to name all who did -- or be charged as accessory.