Some are blaming the father, but I can see how two boys fooling around could accidentally let it go.
I'm not blaming the father...really. But if you have little boys - and have seen them in action...I mean they do get curious and have more ability than common sense MOST of the time. Being mom to three of the little boogers - I would never park a balloon they could possibly get inside and float away in, in my back yard...UNLESS I had them locked in their rooms and the windows nailed shut.
I am sure that is not what he wanted to happen...but it seems to me - he either parked it in the back knowing that a 50lb child could not get in it and float away - or - he just didn't think it through all of the way. Maybe he just trusted that his child would obey, not factoring in the possibility of curiosity.
It just seems it could have all been avoided had he parked it in a barn that had a good lock on it. Maybe.