The Mentalist finished the last episode from the third season.
That's all.
Even a child can write and do that sixth season without explaining anything.

Timothy Carter was Red John, Strawberry and cream was the last episode of the Mentalist. 

Red John saying sorry for killing Jane's wife and daughter?
Come on

I've just seen the first episode when Sheriff McCallister appears and I'm sorry but I can see him as Red John. When he loses against Jane playing at Rock, Paper and Scisors it's so pathetic.

I bet all the money you want that Heller didn't knew who was Red John, all the sixth season has been ridiculous.
Heller that's an advice for your next idea, choose the killer before giving clues, you have to know who's gonna be the killer before doing the first episode, and you didn't.