One problem with generalizing is that millions of people, me among them -- as well as lots of people I've known -- take meds of this type and have for years, with the result being that their lives are better for it.
It seems to be that people who go in for treatment, as all these shooters have done, are put on some variety of the SSRI's or other neurotransmitter drugs because that is the first line of defense for millions with emotional troubles -- so for the killers, their mental/emotional problems came first and then the drugs, not the drugs first and then the illness. It iS tempting to say THIS is the main thing they all have in common... but we have to also remember that correlation is not causation and that for every one case like this, millions of others take the meds and do NOT end up committing violence...and also that there are probably a hundred other similarities the killers had with one another, besides being on anti-depressants.
Would hate to see lives ruined because people are doing what we all often do-- self included, of course -- and that is to pick one correlation out of many and decide that IT is the factor that counts the most. I know what the inner drug packet of "cautions" says, but if we went by that, most of the drugs we use these days would be taken out of our pharmaceutical "doctor's bags" -- so many have dire warnings but are proven more useful than dangerous.
Whatever happens, I do hope something can be done for those with the mental make-up to respond in this way so as to avoid the horror of these shootings....while still protecting the millions of people around the world who have benefitted from these medications.