Because the gunman who attacked an Orlando nightclub was a security guard, the shooting that killed at least 49 people has raised questions about how the security industry screens employees.

Gunman Omar Mateen alarmed co-workers with claims that he had ties to al-Qaeda and was a member of Hezbollah. One colleague recalled that he frequently used racial slurs and threatened violence while on the job.

Despite those incidents, Mateen never lost his position with London-based security contractor G4S. His most recent assignment was at a residential golfing community in South Florida.

The oversight of security guards varies greatly from state to state, and those inconsistencies have drawn scrutiny. Many states have systems for licensing, but at least six have no licensing requirements at all.