Either we need to redefine what probable cause means and say that police are not subject to it, or we arrest officers right away just as we would with any other person accused of committing a crime. Either we write new laws or enforce existing ones; we cannot have it both ways.
You don't need any indictment in order to arrest someone; probable cause is sufficient to arrest civilians, so it must be enough to arrest police.
Civilians are arrested every single day - including innocent ones - and they must wait until their day in court in order to argue their side of the story. Police officers must be subjected to the same rules.
The United States isn't a dictatorship ruling with a brutal army and an iron fist, so our police departments must understand that they are there to serve and protect us - all of us. And when they do commit crimes, they must be arrested and prosecuted like anyone else, bottom line.