Yeah, the story is pretty sparse on facts. I’d guess a miscarriage of justice, or he beat the guy past the point of reasonableness. The guy’s unconscious and Brill kept beating him with a brick.
Personally, I believe that if you break into someone’s house, whatever happens to you is tough shitski for you.
You break into my house, yer done. Of course, I live in Arizona ;-)
Could the intruder be a jilted lover, former roommate, or other acquaintance? Maybe the guy was trying to get back his own property. There are many details missing.