The taser is his police weapon just like his Glock. And, it was on the ground out of his control. He needed to recover it from wherever it was dropped first and foremost. Before CPR, before anything else. Guaranty it is standard police training.
If it’s SOP to get control of loose weapons rather than to preserve the scene (which makes sense if the scene isn’t secured), and if a spent taser can be considered a weapon, then his action seems justified.
That’s what I was thinking- there was somebody else in the perp’s Mercedes... could have been coming up right behind him and the officer, he HAD to retrieve the taser gun
And how would he ‘plant’ the taser by the disabled perp with the other (black) responding cop already arrived at the scene, next to the perp...?