The problem is that there are thousands of people out there who appear like JH did when they meet with psychiatrists and other mental health providers. And only the tiniest percentage of them ever go on to do something like this.
No one expects people like JH or Elliott Rodgers or Adam Lanza or Kip Kinkel or the Colombine killers to do what they did. And there is a good reason for that - the odds that someone will do such a thing is infinitesimal. It would be odd if we walked around thinking that people we know might commit mass murder.
Looking at each of these killers after the fact, we see the signs and they look like red flags. But that is only with 20/20 hindsight. It all looks so clear in retrospect, but what family would ever think their child is going to go on a shooting rampage?
JH's family did not have any guns, nor does it sound like they had any reason to think their son would ever have a gun. Nor did he have a history of violence.
The confounding issue with these types of shooters is that prior to the shooting, most of them don't look that much different than many other people their age who have depression, social anxiety, etc. It isn't until they find a way to commit a shooting that they suddenly start to look different.
I personally cannot imagine that his parents would do nothing if they had any real sense that there could be something seriously wrong with JH. I mean, he was always socially awkward, and now he was in grad school. They probably thought that he was going to turn things around - similar to how Elliott Rodgers parents thought that about him going to school in Santa Barbara. They never had an inkling that he could be capable of something like this. For them to make the leap that he had expressed thoughts about "hating people" to him being an actual threat to others... I am not surprised they didn't.
Now, with all that... here is what I will say. Given that we are learning about how these shooters operate (sadly as more and more of these incidents occur)...I do think that families with young males who are presenting with these sorts of issues should start to consider that its possible that their child could do such a thing. Incredibly unlikely and rare, but possible. And if they have a child with clear social or mental health problems, they do need to make sure that child does not have access to guns.
In the case of Adam Lanza, his own family provided him with those guns. Same with Kip Kinkel. But Elliott Rodgers bought them without his parents' knowledge, as did JH.
When these kids are a bit older, out of the house, and have some independence, and access to some money, that is when it gets more difficult.
I wonder what would have happened if during the time he was amassing weapons if his parents had decided to drop in for a visit. For some reason, I can see JH telling them that he is just too busy with studying for exams, and turning them away.
Anyway, there are some interesting documents about Kip Kinkel you can read here:
http://www.pbs.org/wgbh/pages/frontline/shows/kinkel/kip/ - it has the information about the counseling he was getting for anger problems - you can read the case notes from the psychologist who was treating him prior to the shooting here:
http://www.pbs.org/wgbh/pages/frontline/shows/kinkel/trial/hnotes.html
