Hm, I don't know if it's justified. And, my point is that instead of joining another growing horde of ignorance, we should step back and wait for facts to be revealed before making any kind of judgements.
I will tell you that it appears as if his right hand is not secured, and one can easily fire a gun from a supine position. We don't know if there was a gun, and if there was where it was. Taking some hypotheticals...if there was a gun and the dead guy reached for it, are we expecting the Leo to wait for him to grab the gun and point it at him before he is justified to shoot?
As far as the "belly to belly suplex", it sounded as if the taser had been deployed to no effect. Which, the next thing is going hands on. That's the way it's done.