The answer to that is, we are going to have to go down the path of forced institutionlization. Sometimes locking people up and throwing away the key, that is really the only way you could control them.
Actually, it's not even confirmed if Adam had Aspergers. (That's new to me.) That's good news for those with aspergers or autism, hopefully no stereotypes of them being violent surface. Raises questions over what mental illness he really had though, and that lack of info would hurt any panel discussing what illness is needed to lock a person up.
Who among the mentally ill are actually violent and aggressive and suicidal enough to do these killings? I don't know, and I don't know how they got to that point. Maybe there was abuse in their childhoods, hate from the community, and other things making their mind adapt to violence which warps their thinking as well to favor these mass killings. At the moment, it's not convincing to me that forcing mentally ill people to be in jail would actually work. If it does work, maybe it expands the government budget too much, or it can be used as a tool of politically connected to lock away his enemies by claiming someone is ill. Still, I would expect some to slip through and continue the killings.