Since the store is already close-- there's no point of having the employee to come in because as a security guard, it is best to protect the store and having to protect it in a way that a person shouldn't be let in when it is already closed even if the person looks like someone who is working in the store. If the employee has some excuses as to why he or she wants to come in, it best to respond in a way that he or she should come back when the store opens or during his or her shift.