Are anti-depressants unique to the Unites States? For the most part, spree-shootings are.
Suicide is a bigger killer than shooting sprees but SSRIs have been implicated in very much higher risk of suicide among people taking them. They have also been linked to violence and violent psychotic episodes. Some people think it sounds crazy that a prescription drug could do such things because a) it's a prescription drug, b) it's been tested and approved, c) no doctor would prescribe stuff it it was that bad, and d) pharmaceutical companies would never sell a bad product.
A) While it IS prescription, there are other drugs that are also SSRIs, that is, they work by the same mechanism of inhibiting re-uptake of serotonin in the synapses. Cocaine is the biggest recreational SSRI and episodes of aggression and psychosis are known side-effects. Killer crazy is bad, but killer crazy with guns is worse.
B) Lot's of things have been tested and approved that are not safe. Drugs are tested by the drug companies themselves and drug development is notoriously expensive. If a drug isn't outright lethal there is a cost/benefit analysis (benefit to the company, not patients) and if it looks like the company can recoup the cost without too much risk they can usually find the right people to stamp the approval.
C) Doctors don't necessarily know what's good and bad. They tend to get most of their drug information from drug sales people. They tell the doctor what the drug is for, what kind of symptoms the people who would benefit will present with, and they will guide doctors away from blaming the medications when things go wrong. Individual doctors generally don't see enough patients to see the statistical patterns. Doctors are also really bad at reporting side-effects, partly because they are busy, partly because the patients report the "wrong" side-effects, i.e. stuff other than what the sales people told them to watch for.
D) This one I don't even need to answer, do I? Vioxx is just one of a long list of drugs known to have lethal side-effects that were filtered out of company testing. AIDs tainted blood products knowingly sold, deadly implants, anything else that can make a buck. If they're dead they can't sue. If they're dreadfully sick they can't afford to sue. If they were mentally ill before treatment then they're crazy now so pay them no heed.