while demonstrating gun safety in front of a group of kids.

As you can see in this video, he does so after insisting he is the only person in the room "professional" enough to handle a Glock. Uh-huh. To his credit, he immediately checks if everyone else is OK and goes on with his presentation, turning his misfortune into an object lesson.

Anyway, according to the Urban Legends Reference Page, this event did happen as it is represented in the video.