Final answer:
The guard should not intervene directly but should call the police to handle the situation since the suspect is not on the property.
Step-by-step explanation:
When a guard is informed that a banned former employee is causing a disturbance in the parking lot, and upon arrival the suspect is observed standing off the property, the guard has limited options. Since the suspect is no longer on the property, the guard does not have the legal authority to arrest them for trespassing. The most appropriate action would be option 4: The Guard cannot do anything legally as the suspect is no longer on the property, but the Guard should call the police and report the behavior. It's important to document the incident and the behavior of the suspect even if they are not currently on the property, as they could pose a future threat or return to the premises.