I want to say "probably" driver error, but the fact that he may have steered to avoid cars and because of that chose people pretty much proves he's an idiot and probably undeserving of a drivers' licence in the first place.
"Unintended Acceleration" doesn't mean the vehicle is the cause; it just means whatever happened wasn't intended. Some people have a disconnect between brain and body.
Physics tells us that a vehicle's brakes can always overcome it's engine, but time is critical with any stopping action so precious seconds can lead to disaster. Slow speed operation is actually more dangerous as there must be some reason why you aren't free to drive at speed in the first place, so you may not have the luxury of distance or maneuverability to keep safe outcomes preventable.
Still, being overwhelmed by his situation meant poor choices and reveals poor driving skill.