Frat blood thicker than Family blood?
OR
He knew there was stuff in the house that would make his brother look bad and wanted it removed before the cops found it.

We do not know what was removed from the house if anything was but I strongly suspect that there was stuff they did not want found by cops inside.

It could be anything like drugs, guns, sex toys, sex tapes, secret video equipment or videos they were using to blackmail other people around the area. If they had videos of cops trading sex to keep from getting tickets or arrested, that would be huge considering what happened with the cops doing that same thing at WSU and getting caught.

Cops could have been told they had been videoed and went in that night to find the videos and to shut up any of the girls that may talk, leaving the 2 that tipped them off alive. (I doubt that is what happened but officer Payne gives me bad vibes)