The stupidity applies to both the store and the policeman, however, the store clearly bears the burden of responsibility. The police officer will bear the reality of shooting off his own finger due to his stupidity of assuming the gun was unloaded. Always always assume a gun is loaded and handle it accordingly.
I believe the “Swiss cheese model” applies here, if anyone cares to take the time:
“Every step in a process has the potential for failure, to varying degrees.”
I see several steps that obviously failed.
http://patientsafetyed.duhs.duke.edu/module_e/swiss_cheese.html