if you look at the dead perp you can see they werent all center mass....and yes..he is damn lucky no one got caught in the cross fire
I think what happened is the first return shot disoriented him because he wasnt expecting anyone to be shooting back that fast....and that gave Hero precious seconds to finish him of
As would be expected when the shooting started people were running outward toward the stores hoping to not get hit. I get the impression that after the hero knew he hit the shooter, the shooter started retreating to the bathroom and Eli finished.
I think you are right about the shooter never expected to be trying to defend himself. Maybe not even sure at first where it was coming from which gave people time to get out of the line of fire.
The arms may have been positioned in front of the murderer's body when they were hit. An autopsy may be able to tell from the entry and exit wounds what position the arms were in when hit by righteous lead.