Mass murderers are springing forth more frequently from the ranks of ordinary citizens here in America. Sometimes their family and friends report the rampage as totally unexpected – the killer was quite normal, friendly and well liked by others. Sometimes the mass murder was known to be a bit of an odd bird – a loner or an introverted person. 
Often overlooked in searching for the cause of the violent outbreak is the killer’s use of SSRIs when motivated to commit a mass murder.
What are SSRIs? The letters stand for Selective serotonin reuptake inhibitor. 
They are the common anti-depressants with the brand names Celexa, Lexapro, Luvox, Prozac, Paxil and Zoloft. 
The theory of an SSRI goes like this: 
The brain cells (neurons) have messages traveling along them and when a message gets to the end of the neuron it has to jump a gap (synapse) to get to the next neuron. To keep the signal going across the gap, the neuron releases a tiny amount of a chemical (a neurotransmitter) into the gap between it and the next nerve cell which allows the signal to cross the gap. (Serotonin is one such neurotransmitter.)
The original neuron then takes the chemical back into itself to be prepared to repeat the process when the next signal comes along. (This is called re-uptake.)
The theory of SSRIs is that some people’s bodies are low in certain neurotransmitters such as serotonin and thus need some “help”.
An SSRI supposedly slows down the process by attempting to inhibit the re-uptake of serotonin back into the original neuron, with the idea that it will then be it more likely that enough serotonin will build up to send along the next message. 
Mass murderers, however, seem to still get their signals crossed while on SSRIs and have committed horrendous acts while under this influence.
For example, a man named Robert Stewart back in 2009 in North Carolina had been taking the SSRI Lexapro for two weeks when he decided he would go visit his wife at work. He shot up her car windows in the parking lot at the Pinelake Health and Rehabilitation Center in Carthage. He then went looking for her inside and, re-loading his gun every three shots, he hit 11 elderly residents of the nursing home at point blank range. He killed 8 of them.
His defense attorney stated that Robert Stewart was “full of remorse but couldn’t remember anything.”
This SSRI clearly did not assist in neurotransmission but in mass murder. 
Before SSRIs first appeared in 1988 with the creation of Prozac the number of mass murderers (those killing 4 or more people in one continuous event) were rare in the USA.
The 1980’s and 1990’s saw twenty such cases.
From 2000 to 2012 we’ve seen 26 cases of mass murderers here in this country.
As far back as 1997 a Harvard Medical School study found that 82 per cent of the benefits claimed by the use of SSRIs was indeed something they could dismiss as a placebo effect. Psychiatrists today cannot explain precisely how SSRIs work or prove by normal medical tests that their theories of how they function have any validity.
They can, however, continue to sell more and more of these SSRIs with more and more profit for their industry. The cost to society is great as in the Robert Stewart case- 11 family tragedies and a $550,000 bill for the citizens of North Carolina to try the case in court..
http://www.offthegridnews.com/2012/08/14/psychiatric-drugs-and-mass-murder-exploring-the-connection/
http://ssristories.com/show.php?item=5130