I think that Brett Partidge was the Red John killer (the individual who actually did the killing) and was either the son of or connected with Bret Stiles since a very young age (as he was the individual on the Visual farm we learned about last season). Now, Stiles would want to protect his son/apprentice (whatever he is) so he used his influence with the church and his money to buy off FBI agents, recruit church members, and put people in positions of power to help protect Partridge (Red John's disciples). These people include the likes of Gale Bertram, McAllister, and the other suspects. However, despite their promises to Stiles to protect Red John (Stiles may have helped them get there positions in law enforcement, etc.), as Jane narrows down the list to 7 suspects they realize that their plan has become too risky and they may all be implicated. As a result, they decide to kill off Partridge and the people who have information that could incriminate their entire group. So, they lured Partridge to the house with a promise he could kill Lisbon and, instead, killed him. Then they had one of them call Jane (using the voice changer Partridge used for his Red John voice) and say the line "Lisbon can't come to the phone right now" (thinking that they've covered up all the evidence and are sending Jane on a wild goose chase for a serial killer who is already dead). This would explain why "Red John" didn't kill Lisbon, because it was Bertram and Haffner and the others...all people who like and respect her.

Of course this is all speculation...but it does explain the "He is mar" clue as "He is many". It could also explain the conversation we just saw in S6E2 where McAllister and Agent Reede are talking to Bertram and ask him "how much Jane knows"...hinting to the fact that they're all involved somehow. Bruno Heller has also said that following the conclusion of the Red John storyline, the show will have another direction to go in (and the conflict with Stiles and Visualize could be that direction, as Jane didn't get his chance to exact revenge on Partridge/RJ so he will want to exact revenge on those who enabled him).