I believe you will find kraigwy's position state here where he believes that being held at gunpoint means you have the advantage, yet strangely officers and CCW people still have their guns up when dealing with bad people.
That's true, but there's surprise factor on the other side, too. For the most part, victims aren't expecting to be victimized, and even if they've got a hinky feeling, the instant the suspect initiates an attack is still a surprise.
I don't know that it is surprise as much as it is an unwillingness for so many people to not want to harm another person. Take the vid here...
From the sounds of the video, the cop had exited his car and given the commands he was issueing (with others) before Spencer exited his vehicle, the cops would have had their guns draw after the prolonged chase. Yet for various reasons, they did not even begin to fire at the stumbling and spastic Spencer until it was too late. Why they would have hesitated could be for many reasons, but I would be inclined to believe that it had to do with recognition of the situation, realizing that Spencer wasn't attempting to flee on foot but was armed with a knife and running to attack officers. These officers had their guns out, but were not actually prepared to fire.
In other words, for the Tueller drill at least two of the first three steps of the OODA Loop sequence are accomplished before the drill starts. These officers had to go through all 4 again before firing and probably lost considerable time during observation in trying to figure out what the guy was doing (flight v. attack) and then deciding on the course of action.
The attackee is just waiting on the que to be Observed to start to react be. He is already Oriented before the drill starts and has already reached the decision that he would draw and fire when que'd.
In this example, the bad guy covered 22 feet. On one of the forums, I read that the shooter was a trainee, but with considerable combat experience in Afghanistan. Of course, all the other cops present weren't trainees. The video does show some of the shock in the trainee's voice about having shot the guy.
We have run kraigwy's in various ways. The person drawing on the drawn gun is the one that tend's to die the most.