Bzzzt! Incorrect, Danforth! Thanks for playing....
The criminals through their act set in motion the events. The customers have a right to detain them. They were committing a crime, anything that happens as a result of that crime, is their fault. If they speed away and cause an accident, even if they didn't hit anyone... If someone wrecks to avoid them.... It is their fault. If someone tries to detain them and they try to kill them with their car... It is on them if they get shot and killed by the person they were trying to kill. The person trying to detain them was doing nothing wrong, while they were. That's just the way it works.
I can see you want to just let them go.... That's fine. When you witness a crime go ahead and ignore it. But these folks didn't want to allow them to get away.... And don't have to let them get away. The bottom line doesn't change. They choose to steal, they chose to try and kill someone. They made the poor choices, they get too live with them... Hopefully in jail for a long time.
If it's determined the customer discharged his firearm negligently, then he goes to jail to. No problem. But nothing in this story indicates it was negligent.
I can't even nerve I am going to entertain the stupidest question on this thread but here goes:. How will the police determine who the criminals are and who the good guys are when they roll up? The police would be there nexus they were called too the scene..... And the caller will have provided them the information.... Two guys in the car, with contraband, surrounded by six guys with guns. Chip arrives, everyone drop your guns.... Everyone complies, and now bad guys go in back of cruiser.
Not so hard.