Lest it be forgotten, this mess is still hanging fire, too

In March 2016, the Deschutes County Sheriff's Office and FBI announced that an FBI agent was suspected of firing twice at Finicum and may have gotten help from four other FBI agents in covering up afterward. No other agent has been charged in the case.
 So, if the other agents helped him, they're guilty as well, so why the hell HAVEN'T they been charged?