The original founder of the site explains his relationship with Karpeles in an interview with Ars Technica.
I met [Karpeles] I think on bitcointalk.org. The Bitcoin community was very small at that time and I asked him to do some software development for me. He did that task and I was looking for someone else to run Mt. Gox so I could focus on other things. We discussed the possibility of him buying Mt. Gox from me and I ended up selling it to him in 2011.
I have not had any involvement with Mt. Gox other than as a minority shareholder since early 2011 when I sold it to Mark Karpeles, whom I have never even met in person,” he said. “It is my understanding that Mark also rewrote the entire codebase sometime in 2011 shortly after the sale and none of my code remained in use. Aside from the sale, I have never received any distributions or profits from Mark
McCaleb also tells Ars he lost around $50,000 (held in dollars, not bitcoins) when the exchange closed.