I think it is Patrick Jane's father, upset that Jane ran away from the carnival thus leaving him without an act.  Jane WAS the act.  Without Jane, his father had nothing.

Jane always refers to Red John as a performer and someone who is equal to his talents.  Who better than the man who trained him, his father?

This would also explain the reflection in the computer screen when Jane is talking to Red John.  Many people say the reflection looked like Jane.  Well, that would make sense if Red John is Jane and they cast an actor who looked like he could be Simon Baker's father.
Also, the way Red John wants to be close to Jane and even have Jane follow him is almost fatherly, in a weird, psychotic kind of way.