I like that you included the tag "murder".
I feel for the girls family and friends and can imagine how angry they must be. Suicide is hard enough to deal with and process without having the fact that someone assisted your loved one in the act. The part that makes me sick here is that more than one person knew about it ahead of time and nothing was done. i.e., the friend he texted. That, and you know he had to have persuaded her to follow through with it.
I'm in Utah, a bit north of Utah County, and remember hearing about this when it happened. Just read the latest article in the paper and am glad to see what they are charging him with and that his court date is right around the corner.
Still doesn't help her loved ones get her back, but...
Obviously there is a problem with the parents. Shitty parents = shittykids
Probably, but sometimes good parents can raise shitty kids... Sometimes a persons brain can be that abnormal. But it's likely that you are correct. The boy probably experienced some severe trauma or neglect in his childhood. That is how it usually is...