I've been a father so I'm well aware we can't watch our kids 100% of the time. However, if I left the keys to my bulldozer in it and my 6 year old climbed up in it, turned the key, and proceeded to bulldoze my house down it would be MY RESPONSIBILITY. The parents need to be held responsible for this ridiculous drama. Things like this happen every day. They just don't involve balloons and the national media. I'm sure 80% of the story we have is probably wrong but from every angle I come back to the father being at fault.
Should the kid be punished? I think so but in an appropriate way. I doubt he can understand the significance of what he did, assuming he actually did it. Again, fingers should be pointing back at the father.