The cops did it because they are furious about a reprisal killing, and they are exerting a bit of social and political pressure on the judge not to give him bail or let him off. They're basically letting the judge know that this guy is their #1 target.

Most judges pretend to be independent arbiters of the law, but as we can see, no such judges actually exist, so we (literally everyone, not just cops) are left with having to make political statements to the judges in order to demonstrate the amount of political stamina and capital we are prepared to use to secure convictions.