I would too. Don't misunderstand me. If they are guilty then punishment is surely in order. But, if they are only partially guilty of an administrative violation, then the punishment should fit the crime.
THey are certainly guilty of filing a false report. But that wasn't what they were charged with, nor is that WHY they were charged.
The shot a guy who was running away from them. That is what they were charged for. The false report was used as evidence against them, because it is consistent with a coverup, as is the collection of casings and throwing them in the canal.
They may have had valid excuses for those acts, both of which violate procedure (a procedure put in place largely to help protect agents who do the right thing, by telling them exactly how to do things above-board so that they can be cleared).
But their actions are also consistent with what people would do if they were trying to cover up a crime.