One day at the range after teaching an NRA class I turned from the line to see a guy walking towards me stuffing rounds into a Ruger SA and muzzling everybody on the range AND in the parking lot. As he approached me with his gun pointing at me he snapped the loading gate shut and the gun fired a round right between my feet. And this guy was a County Sheriff's Deputy. He just laughed. 3 or 4 times a years their entire department would use our range for qualification and those guys were the scariest people I have ever seen on a range. No muzzle discipline at all. After that as soon as they all pulled in I would pack and leave. Keep your eyes peeled around people you don't know well. Especially if they're "highly trained professionals".