According to his wife, mother, and brother, he was battling depression and having trouble with his medication. He had no previous history of violence.
His wife, mother and brother also don't believe the killings were in response to any grudges Drake may have had.
"We do not feel these tragic killings were premeditated, a political statement regarding pro-life or pro-abortion factions, or out of a grudge. We have been overwhelmed by sadness and emotion as we try to understand what happened and why."
I googled 'SSRI psychosis' and hit this scary site.
This website is a collection of 3300+ news stories with the full media article available, mainly criminal in nature, that have appeared in the media (newspapers, TV, scientific journals) or that were part of FDA testimony in either 1991, 2004 or 2006, in which antidepressants are mentioned.
Antidepressants have been recognized as potential inducers of mania and psychosis since their introduction in the 1950s. Klein and Fink described psychosis as an adverse effect of the older tricyclic antidepressant imipramine. Since the introduction of Prozac in December, 1987, there has been a massive increase in the number of people taking antidepressants. Preda and Bowers reported that over 200,000 people a year in the U.S. enter a hospital with antidepressant-associated mania and/or psychosis. The subsequent harm from this prescribing can be seen in these 3300+ stories.
Harlan Drake has been ordered to undergo psychiatric evaluation.
I'd say that is an excellent idea.