Comment Fire code violation (Score 3, Informative) 150
You cannot lock customers in. It is a safety issue.
The doors MUST open when pushed against. Even automatic sliding doors have safety hinges that allow you to push them open in the event of an emergency or power failure.
Beyond that, refusing to let someone leave could constitute false imprisonment.
Locking yourself in a store with a criminal is a good way to escalate a situation to violence. Sounds risky for employees and other customers nearby.