Under what circumstance can a security guard make an arrest?

The correct choice is based on the principle of citizen's arrest, which allows individuals, including security guards, to detain someone if they directly witness that person committing a crime. This authority is typically granted in situations where immediate action is necessary to prevent further harm or criminal activity. Security guards, trained in their roles, have the responsibility to protect property and individuals; thus, witnessing a crime gives them the legal basis to intervene and detain the suspect until law enforcement arrives. This ability to act is crucial for maintaining safety and security in various environments, such as retail stores, public venues, or corporate properties.

The other options involve scenarios that may not legally empower a security guard to make an arrest. Being authorized by an employer does not inherently grant arrest powers unless it is coupled with witnessing a crime. Working alongside law enforcement may offer additional backing but does not provide the authority to make arrests independently. Feeling threatened by an individual's behavior might prompt actions for self-defense or safety, but it does not legally justify an arrest unless a crime is actually witnessed. Understanding these distinctions is vital for security personnel to operate within their legal boundaries while performing their duties effectively.