The cop isn't disoriented at all in the videos.
Let's change things up a bit. The same scenario unfolds, but in the struggle instead of grabbing the cop's taser and using it on him, Scott pulls out a knife and slashes the cop or a hammer and bashes him a good one. Tasers can be just a lethal as many other weapons. The cop is on the ground and then Scott starts running.
Maybe the rules are the cop still isn't supposed to shoot Scott. But if the same thing happened to me as happened to Slager, I'd be mighty irritated to the point of shooting Scott.
Then you would, and should, be facing criminal charges because irritating a police officer is not a justification for shooting someone. Let's remain on planet Earth. Slager is not harmed. He has not been tazed. Scott has no hammer or knife or any other weapon. He is running and is 20 or 30 feet away from Slager when Slager starts shooting him. Where is the threat to the safety of the officer or any other person?
I agree that Slager didn’t get tased. But apparently Scott did fight with him and seems to have taken the taser from him. That is what reframes the situation. If you’re willing to do that, you’re a potential threat to other people. I don’t know if it fully justifies what Slager did, but it muddies things up enough that I’ll be surprised if the murder charge sticks.
Notice I said we don't know all the facts, and if Slager was not disoriented, it looks pretty bad for him.
But if Scott did in face taze Slager, any jury might give Slager a lot of leeway. How about we let all the evidence emerge before making a final condemnation?