“Why did they get him back out and pin him on the ground?”
That’s a good question that will get answered at the trial. Until then, people can make up whatever they like, and they will.
I spoke to several relatives who are Police Officers.
My cousin George told me that once you have the cuffs on someone, their safety and life are in your hands. What about, I asked, a suspect who is cuffed and in the backseat who start kicking, biting stuff, etc.?
He said that you take them out and make them SIT on the ground. Not lay. Sit. If they do not comply you can use several ways to keep them from rising up (pull on the arms, push head down, etc.) but he said the last thing you would do is make them lay facedown and push their neck or head into the ground. He said that’s not done, training is explicit not to do so. You can put your knee or weight on their back, but never, ever the head or neck.