Brett Patridge was killed because Red John wanted to keep Jane busy by showing him a corrupt organization (Tyger Tyger) or maybe trying to imply RJ was member of that organization, that's why Red John let Teresa alive, he wanted her to "send a message" to Jane, the message was what Patridge said before he died(?) (Tyger Tyger), now with the detective death and the tattoo is the same thing: he is trying to confuse Patrick.

is red john killed in episode 8 like some guy on here said?????? i blumin hope not!!!!

Here's a Red John clue no one has mentioned yet from 'fire And Brimstone' (season 6)

Ray Haffner is on the phone with a client while walking into the diner to meet Lisbon.
We overhear him say, "listen to me Don, you don't have a mistress, you have a vindictive screwball that is about to ruin your life. [don replies] yes, well it's very lucky for you my job is to fix problems. so here's what you're gonna do: You are gonna write her a check-- It is gonna be a very big check-- And then you are gonna pray that this problem goes away. [don speaks]
If she doesn't, don't worry Don. There are plenty of ways to keep a woman quiet. OK? Ahright. I gotta go."

Clearly Ray Haffner has no problem killing a woman if she is a "problem".

    "Surveillance" is the word best describes both the work of Red John and Ray Haffner. Red John is a professional serial killer. He does not want to make any mistake, so do his work best by following his targets like a shadow and study about their routine before he makes a move to kill them. Ray Haffner closes cases through "creative surveillance techniques" as mentioned by Lisbon in season 4 episode 2 and we have seen him doing that not only he bounds Cho to keep an eye out on Pattrick but also when he goes to Bertram to seek help to monitor the list of people on the red fake diary imitated by Pattrick which belonged to the victim of the same episode to throw Haffner out of the trail in order to solve the case with Lisbon to help her to get her job back. So both these people put on for surveillance before they move for their target.                                                                                   Besides Haffner has friends in FBI since he used to work their before. So it was easy for him to get to know that Pattrick did not kill Lisbon and Rigsby in the season 4 finale when FBI Agent Darcy claims that Lisbon and her team are playing them.

Reasons

1) Haffner is in visual, the right age, and was supposedly at the farm when RJ first killed.

2) S6EP6 27:55. Watch his face go blank when he reads Patricks text (Patricks address).

3) They split the suspects into two groups. 1 of the story line from Season 2 and 1 of the story line for the future of the show. 

Some fairly unnoticed points that need to be explained:

1. Why is Haffner so interested in the Red John case? He referred to a client who's interested in the case. Logically speaking there are only two possibilities, First, he is Red John and there is no client. He is not Red John and there is a client. But who is the client? Visualize? Stiles doesn't seem to be interested in the Red John case, why would Visualize be? Is the client Red John himself?

2. Of what nature was Kirkland's relationship with Bertram? They seemed to be close. Apparently Bertram is a member of the Tygers, and apparently Kirkland was after the Tygers. So was Bertram playing a role and fooled Kirkland? If that's the case why would the Tygers let Kirkland get close to Jane and the Red John case? Or was it the other way around. Or maybe Kirkland is a high-level member of the Tygers about whom only Bertram knows, and they faked Kirkland's death, Which could make it possible he is Red John.

3. How did Stiles know the whereabouts of Kristina Frye?

4. Is Rosalind trustworthy? If she is, why didn't Jane take her description
into account? If he forgot to do that then he's incompetent; if he
didn't and the producers did, then they're incompetent. If she's not
trustworthy, why did Jane ask her whether Timothy Carter was Red John or
not?

5. Is Alexas Shultz a Tyger member? If she was then why would she work for Kirkland? Would that confirm Kirkland was a high-level Tyger member? Or possibly Red John himself? If he is Red John why would he kidnap men from Jane's fake list and ask them if they're Red John?!

6. Why didn't Jane set a trap when he knew Red John was going to kill James Panzer(aka the SJK)?

And many other unanswered questions.

Partridge = Flashback ---> Green
Partridge = Red John   ---> Red