To me, the kicks to the head are well beyond "adrenalin rush".
You mean the ones before they had him restrained? Maybe. I think the rifle cop was trying to stomp him down to keep him facedown but did appear to bounce his head off the floor. The rookie pistol cop was trying to do everything the rifle cop was doing, but weaker (head stomp and muzzle punches).
Again, though, the context was that he had
just shot at them and then run into an occupied store. At that stage as far as they knew they were still dealing with an armed, unrestrained, unsearched active shooter.
Once he was restrained but before the officers had searched him he tries to roll over and the rifle cop kicks him once in the shoulder blades.
As we've discussed before, head blows are no joke. We've talked about how antifa that have hit cops on the head should be punished. Cops repeatedly kicking a guy in the head should be punished as well, IMO.
In hindsight we know that at that point he had already put his gun down so we can see his surrender as genuine. If I consider what the responding officers knew in the moment, I see it as less black and white as you apparently do. They had narrowly survived being shot at by this guy, were running after him into an occupied building (as John correctly points out, sacrificing solid tactics for expedience as we demand of our police in an active shooter situation). They saw him apparently giving up but did not yet see the pistol on the counter, nor if they had could they assume that was his only weapon. The guy was mere seconds into his sudden retirement from being an active shooter and apparently his retirement notifications hadn't made it to their inbox.
I'm not saying there is no room for improvement. I'm not saying every move was perfectly how I would script it. However, given the totality of the circumstances I wouldn't say their actions are in any way comparable to the Tyre Nichols murder. Absolutely, and unreservedly not worse.
The most complete video I've seen is here:
https://www.youtube.com/watch?v=T_FkTV4RVr8