For one important thing, the agents DID report to their supervisors and were given the option to go home as it was the end of the shift, or wait a few hours. There was no 'cover-up'!! The truth will come out when the transcript is read.
That is incorrect. They only "reported" it when other agents brought it to the attention of the local supervisors. By that time, they had attempted to "cover it up" by collecting all the shell casings and disposing of them.
Stop confusing people with facts. Next we'll hear that the guy wasn't actually shot from teh back. Oh, wait...