This angle clearly shows one of the agents running away from the scuffle before the shooting carrying the victim's handgun, a Sig P320.

Your description is not accurate from my perspective. The first shot comes from behind the victim. The agent fleeing is responding to the gun shots, not before. That agent bolts from the first shot from close range. Once the victim went for a gun the agents were all trying to remove it.

It seems like they took the gun from its holster and then shouted "gun". Its like Renee Good. There is plausibility that the officer hearing " gun" reacted... But theyhshot him many more times after that.