I expected them to do something like confiscate the video. I guess they were so thrilled and excited at their kill they still had tunnel vision. You can rest assured that in the future cops will learn from this and be a lot more diligent about searching out potential witnesses and destroying incriminating evidence after they murder someone.
Nope, the white cop ran back to pick up the taser and tried to surreptitiously drop it next to the perp/vic without the black cop noticing. He was focused on controlling the perception of what happened and concerned about the other cop. The black cop was busy attending to the perp/vic.