"Zero tolerance" results in a lot of bad decisions everywhere.
The chain outfits don't allow any independent thought for local managers, they aren't interested in common sense applied to the moment whether its a holdup or scheduling an extra dumpster pickup. That's a big problem in many of these situations. If you think about it, it says AutoZone is more interested in legal CYA than the safety of its employees.
If the police think the robber is responsible for many other hold-ups (30-40), then there must be a string of dead bodies if the statement that the employee saved the manager's live is true. Of course he didn't know that at the time, so I think that part is immaterial to judging his actions, but it is speculation for an intended agenda.
He should not have been fired, but at 23 years old, he learned a valuable lesson about who not to work for.