To be honest, the ferocity of the attack led me to believe that the deer had personal issues.
A few weeks ago, I hit one with my car. It must have been a glancing blow because when I pulled over, the deer proceeded to attack my car in much the same manner as this video, forcing me to drive away from the scene. It's a good thing I did not get out of my car or I would have been mauled myself.
Struck deer attacking motorists is actually quite common. When you hit a deer, unless you killed it, do not get out of the car under any circumstances.