But what I am asking is, where does the blame and guilt rest?
Nowhere. There is a reason why the Swedish, and other nations', laws don't punish 10 year olds.

This begs belief that any person would leave a child of 4 years old in a play area without adult supervision, or for that matter a 10 year old. Yes it is a tragic event, but in my opinion it was one that could have been prevented.
How? By locking them up? By confining them to their room (after searching it for any remaining pieces of rope, of course)

Also, supervise a 10 year old child at all times? Really? And when does it stop? When they're old enough to look after their parents in the nursing home?