A SUNY Albany alum told CBS News that Markoff talked about going to strip clubs, but never mentioned visiting a prostitute. He said he got in many arguments with Markoff about his misogynistic attitude towards women.
http://www.cbsnews.com/stories/2009/04/20/national/main4958272.shtml
My (uninformed) guess at this time is that he’s a self-loathing poofter and could not deal with it. As far as him being pre-med, I bet his grades were in the crapper.