as a form of protest / activism. There was a movement a while back for the "empty holster" campus carry thing. It's been a while since I've heard anything about it (not spend much time on those forums lately) ... but it's a possibility.
I have been known to leave my empty holster exposed after removing my pistol in a few places where I have to be disarmed and am feeling particularly resentful for that fact...but trust me, I don't wear a badge, sash, tiara, or CCW T-Shirt
Of course that doesn't explain the rest of the whole picture...sounds like it would have been a bit of a spectacle with or without a holster/badge...