Until the robbing thug perp is pronounced dead on the scene he’s a mortal threat. Moving or not.
You were there?
Here’s the security camera footage,
http://www.youtube.com/watch?v=MJZdFcDmllQ
Watch after the second robber flees after his friend is shot, notice Jerome casually walk back behind the counter, pulls out another gun and then walks back to execute the man. Jerome killing this man was unnecessary and this is why he was convicted of first degree murder.