This is by far the worst injury to result. Reality is. throwing water bottles onto a field at a sporting event is bad, but 99% of the time, no one is hurt and it's not that serious.

Obviously, if you do it you risk that someone is hurt and it can become much more serious. If you secretly confessed to me that you had thrown a water bottle on the field, I'd shake my head and grimace, but think little of it. People have thrown garbage at me from the stands at a football game. I didn't think it was good, but I don't think they went to jail or really deserved to.

Sometimes a dumb, bad thing + freak accident = serious, bad thing. The kid did something bad, but I think tons of people would take the same risk under those emotions.