Thursday night (12/4/14), a man walked into a Red Lobster near the Meadows Mall in Las Vegas with a gun and attempted to rob the restaurant. We don't know why he wanted to rob a Red Lobster; there probably are much better targets out there and live lobsters stuffed into your pants is something that just isn't going to work out well.
Now and intrepid citizen decided this would be a good time to fire a warning shot.
"However, a person in the restaurant pulled out a gun and fired off a warning shot in the air. Police said that caused the robber to take off. " Article here.
Not exactly brilliant. If you have cause to fire a warning shot, you likely have cause to shoot the threat. Warning shots can go wild and injure an innocent person. Not to mention hearing damage and scaring the heck out of other people who don't know what's going on.