[algore]

I understand, but Security guard undoubtedly had many training sessions about not chasing for stealing stupid little stuff.

He either knew and/or recognized them, or they dissed him in some way that required he follow them.

[GaryCrow]

The thief was a licensed security guard. The Home Depot employee that was murdered wasn't a security guard.

The female thief was the one who murdered the Home Depot employee. She had worked as a security guard in the past. The "security guard" is the criminal in this case.