My first thought was of that pharmacist. Memory of that pharmacist story is that the jury didn’t buy his self-defense claim, either, and he got @ 26 years in prison.
That case doesn’t sound as cold-blooded as this one (tho, of course, there is no video or documentation, other than the victim/perp’s statement to the police).
Circumstances do not match up. This guy was trapped in his basement. The Pharmacy guy was able to leave the area to retrieve another gun.