I just don't understand why would Bruno Heller kill one of rare characters on the show that appeared since the pilot and that has been one of people's favorite for Red John role. I refuse to believe he's really dead, at least till i see the next episode.

Here are my thoughts on what might have happened:
1. Besides Lisbon and Partridge, there was another person in the house. Proof: Partridge was locked from the outside in that closet, no way he could have done that by himself.
2. He is really dead. Red John killed him, end of story.
3. Scenario where he might be alive and it was just a trick for Patrick to think he can't be Red John anymore since he's ''dead'' (Something Red John would actually do to protect himself since Patrick is getting closer) -  When Red John is calling Patrick from Teresa's cellphone camera is on Patrick answering and Red John saying something like: ''Sorry Patrick, Teresa can't come to the phone right now, can i get a message?...then camera switches to Red John who is holding his knife with his left hand and wiping it with his right hand while saying: ''No?'' - My question is with which hand was he holding the cellphone? You can notice the ''No?'' is coming from the room where Red John is and the voice does sound like Brett.

Personally, I never thought he can be Red John (I have a solid theory for Bertram and I stick with him), but this was just a little hope for all the people that were and are still believing Brett is Red John.

All in all, even though if he really is dead we can at least say he was Red John's friend. (Tiger, tiger) ;)