Awful. When my daughter was 3, we were playing and she accidentally fell and hit her head on a table. She got a nasty bump on her forehead and was fine.... But I felt SO guilty and terrible that I wasn't more careful.
That isn't even in the same ballpark as this... As a Dad, I feel like it's my duty to protect and keep my kids safe. I don't think I'd ever be able to come back from something like this. Hope things work out for the family here though.