Didn't watch it.
Does the video include the part where the FBI agents lied about taking shots, tried covering up their involvement, etc...?
Of coarse... in typical brave cop fashion... He was shot in the back.
You should have watched it. You would then understand that Finicum was facing a cop who was holding only a taser when Finicum appeared to reach for his handgun that the cops knew he carried in the pocket he was reaching for, and which was in fact found there after the shooting.
You would also have realized that the cops had several opportunities to shoot Finicum dead long before they actually did, giving Finicum every opportunity to stand down and surrender beforehand.
I realize that the two other cops shooting Finicum in the back may appear to be bad form, and that those two cops should have instructed Finicum to turn around so they could instead shoot him in the chest. However, given that Finicum had so far ignored every other directive given to him, and given that Finicum had that day threatened that blood would run rather than him give up, they had no reason to believe that Finicum would do so.
So yes, rather than risk Finicum shooting the taser-holding cop face-on, the other two cops shot Finicum in the back to end any further threat to the other cop. Should they have held to proper and polite form and waited until Finicum had turned around to face them, with that happening perhaps only after Finicum has shot the taser-holding cop dead? If you really think that I really have to wonder what world you are living in.
Does getting shot in the back suck? I'm sure if Finicum was able to answer today, that he would say yes, it sucks. However, by most accounts including Finicum's own words on video, Finicum on that day was quite ready and willing to go down in a Butch Cassidy and Sundance Kid blaze of glory, and his own actions pretty much ensured that it would happen as it did.