A 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.

Every police agency and training in the world will clearly explain that a vehicle is absolutely considered a weapon.

A single rental truck in Nice France killed more people than any mass shooting in the USA, ever.