How is that funny? I just don't see the comedy.
You're standin' around, pumping gas, then get smoked by a 300lb tire rolling at probably a few km/hr, from behind and not expecting it or ready for it in anyway. That's some shitty luck... but not funny.
The way that would have twisted that guy's spine probably put him down for a long time and cost hundreds or more in medical treatment to get to walking properly again. He didn't look like an athlete that could take a hit like that gracefully. It does appear that luckily, he went over backwards and smashed his skull on the concrete as opposed to having his legs crushed between the tires and the pumps. I wouldn't be surprised if he didn't break anything... but he probably sprained alot of joints from his ankles up.
Still not found any funny.