Unfortunately, whether they were on a continued regimen of medication or not, the majority of mass murderers seem to be taking or have taken one or more of these medications. That may be correlative rather than causative, but the potential for a link should be investigated further.
Of all the schemes the government has cooked up to spend the money we haven't been taxed yet, some of the most useful have been discarded--I'd rather the TSA budget was used to provide inpatient treatment for the most violent of the psychologically afflicted than groping people at airports, for instance, and I think it would do more to keep all of us safer--but then, the ugly problem of who decides who is sane rears its head.
I agree that those who summarily decry the concept of institutionalization may be a few brews short of a six pack.
Zoloft, Prozac, etc., are in the class of antidepressants called selective serotonin reuptake inhibitors, SSRIs. Those who inherit a slower version of the enzyme called CYP2D6, those who had a recent increase in the dose of their SSRI and those who happened to take other legal drugs and other legal substances that increase serotonin levels can experience what's called serotonin syndrome. It can be really bad news with physical signs and symptoms as well as psychotic behavior. Pardon the NY Times source, but it explains it very well for the general public.
Neighbor says Lanza was on meds, links between SSRIs and violence
Googling asperger's ssri will get 290,000 hits. That 2nd link has a list of school shooters and other killers as well as suicides on SSRIs. I'm waiting for a credible story about Lanza'a toxicology report.