Intervening/stopping it would have been the HUMANE RIGHTEOUS CORRECT thing to do.
The ROOKIE DEFENSE? Just following orders. Didn't know any better.
What kind of training is needed to stop a murder in progress? Five minutes into the murder one of them says "I can't feel a pulse". Knee in neck murder knees neck almost another five minutes? Really? I see. Wanted to be sure the pulseless handcuffed man was subdued. Gotta be sure. He couldda threatened their lives. FEAR FOR OUR LIVES! Right. Whites seem to be so chicken about this. Cop whites? Deadly.