This is David Millar at the Giro d'Italia, which is basically the biggest race in the world after the Tour de France. Apparently unhappy with his ride, Millar chucked it off the bridge. FanIQ writes:
When you're about to potentially win a stage at the Giro d’Italia… to at least get a sliver of recognition, and your chain snaps, you're probably going to be pretty damn mad.
Forget the chain, man. Did you see how slow all those guys were racing? They should really shift to a lower gear. It's like they were biking through something thick and sticky, like… molasses.