Being on the ground doesn't remove any potential that he could be dangerous.
I don't know why he was being beaten on the ground, that seemed a little excessive. Not sure how many times he was shot, but generally if law enforcement ever makes the determination to shoot they do it to shoot to kill.
They knew he had 1 gun, so he could have 2 guns. The officers don't see the angle most of the camera angles see. They see the perspective they see, from themselves. That is the perspective that will matter by law. What situation were they in and what did they see when they made their decision?
You have the luxury of seeing a perspective the officer did not see, and the officer has the luxury of seeing a perspective you did not see.
People who are in favor of throwing the officer's life away without knowing all of the details are doing basically doing exactly what they're accusing the officer of in suggesting that he threw away this person's life without knowing all the information.
I don't know what Kristi Noem is on about, but she's a political appointee and not an investigator.