Kat, we are officially AT WAR (AUMF 2001 not rescinded), THE WAR AGAINST TERROR, and therefore, the Laws of Armed Conflict apply, in my opinion.

This individual attacking a US Federal Officer is absolutely a "Terrorist", and according to the DOD Law of War Manual, is possibly also an "unlawful combatant", because they are a engaged in attacks against Federal Officers during wartime.
Therefore, the driver of the subject vehicle may have also committed a WAR CRIME.

To my knowledge, "unlawful" or "unprivileged" "belligerents" or "combatants" have no rights under the Geneva Convention and are basically considered equal to SPIES.

It is also 100% justified for deadly force to be used to neutralize any Terrorist threat, especially to stop an attack in progress.

Terrorists using motor vehicles have killed and maimed countless People in Europe in past years, turning cars and trucks into deadly weapons, and that is becoming somewhat of a pattern related to ongoing attacks against ICE.