This is not the degenerate Cubs mascot whose pantsless existence we've all come to know and struggle to comprehend. This is just some bootleg, pantsless, degenerate Cubs mascot who does not enjoy it at all when people remove his head.
This apparently went down at Wrigleyville today and things take off rather quickly. About 10 seconds in, a dude standing behind the bear, decapitates the bear and the dude inside immediately turns around and socks him in the face with a fuzzy paw.
Order is sort of restored and the bear gets his head back when he appears to be hit in the muzzle. More scuffling, and then the bear stalks off before bending down to pick something up by the door. The girl in the background repeatedly saying "oh my god" adds a certain inexplicability to the whole thing.
The Cubs lost to the Phillies, 2-0.
Update: It seems like this is Billy Cub, a bootleg Cubs mascot that Cubs ownership hates and has tried to get rid of. He's apparently been accused of being abusive and racially insensitive with fans before and MLB sent a cease and desist letter on to him on behalf of the Cubs.