The details of the story are vague right now, (and take this with a grain of salt, as a YouTube description is the source), but during a club soccer match in Iran, some fans threw an object onto the field. A player found the object, and thinking it was trash, tossed it off the pitch. As soon as it hit the advertising board it exploded. No one was injured, and the match was called off. Authorities are investigating the matter.
And people say the bleachers in Oakland are dangerous.