alt Hacker NewsA vehicle can be just as deadly as a firearm. And vehicles had previously been used aggressively by the protestors.
There were claims (no idea if true) that the agent who fired the fatal shots had been dragged down the road and injured in a previous vehicle-based altercation.
If him being previously injured affected his mental state such that he needed to kill someone who was not presenting an immediate threat to life, he should not have been on duty.