Suing from the Grave

I am sure that this may be a touchy subject but it seems to me that every time something bad happens we feel the need to sue.

Chicago Tribune | Family of boy killed by train sues Metra

Not let me just say that:
This was atragedy
I have not had a loved one killed in any remotely similar manner
I am sure that the parents would rather have their child back

Given this though, I am not sure what the point of the suit is. The people were fired, they paid a price for their actions. Now I am not sure if criminal charges were filed but even if there weren't, why sue? Is it to send a message? If so then I am missing what that message is. Is it to further punish those involved? Maybe at least a little bit. I don't want to seem callous, but I can't really see what is to be gained from this suit.