Conjecture. Understandable though, as that's the narrative LEO would have you believe.
Neither you nor anybody else who has viewed this video knows for sure whether Finicim was reaching for a gun (after raising his arms in surrender) or reacting to being shot.
It's understandable because it FITS THE FACTS, not merely what someone wants to believe.
A) Finicum regularly wore a 9mm in an under the shoulder holster.
B) Finicum attempted to flee a police stop
C) Finicum pulled his coat back with his left hand and reached toward that area with his right hand.
D) Finicum stated he would not go to prison.
If you attempt to run from a police stop, crash through a roadblock, are know to armed and have publicly stated you will not be taken to jail, you're going to get shot trying to reach under your coat.
We have to ignore all of what Finicum said, and what he did, to arrive at the conclusion he was 'murdered' by the police. He made a decision he was willing to die with, but some on FR would rather believe he was a liar.