Important hint: every single decrypted note contains at least one nickname. See if you can find and understand them all! Some of them are relatively easy while others... well, you have to be a bit creative. They may seem very obscure and even unrealistic but they are actually based on a true story...

What?
Are you serious?
What nonsense is this?

I was actually thinking about shooting Ghorpm PM... erm I mean super duper chat message to ask him about this as I ahve it favourited since the time this was relevant and recent forum change has turned it white again so it was brought to my attention.

Ghorpm, we want solution!

Enjoy.

Lovely.
So older mafia threads will be moved too and I will have to change all links in admin thread? Meh.
Maybe I should post in all of them...

*bursts into room*
NECROMANCY!
Alrighty, let's get the ball rolling, here.

- Son of an Andrew! I hate them! - Might be referring to Anderson, but I'm not entirely sure.
- Buckra is always checking up on me! - If I remember correctly,"Buckra" used to be a derogatory term for "boss" in the South. So apparently, somebody's on to the dude. I'm guessing Sophia, since she's the supervisor.
- Second D forget where is his place! - Must refer to Dennis Johnson. Assuming these notes go in chronological order (which it seems so far), this is the first indication that he hates Johnson.
- Big Jaw is smart. Too smart. He can be a spy or something. - Considering that Miguel chews a lot of gum, I'm guessing he's "big jaw". Him and White might be working together.
- If something goes wrong I will have to ask to kill second D. Too bad! - The indication that he hired somebody to kill Johnson, or is otherwise working together with somebody.
- R's head is literally empty. When you look deep into his eyes you will see his occiput. - Considering that "D" referred to a first name, "Dennis", I'm guessing that "R" refers to Roy rather than Rodriguez, meaning that Spacey has either been drugged or is otherwise just out of it (making his last name kind of a pun).
- Hospital is playing on my nerves again! - Must be referring to Ward. This could mean that either he's watching McCrary as well, or he's in on it and is somehow screwing up the job.
- Wisdom is plotting something! - "Sophia" means "wisdom", further backing up my idea that she knows what's going on and is spying on McCrary somehow.
- I can't believe Spik has a crush on her! - "spik" is a derogatory term for a Mexican, which probably refers to Rodriguez. This further backs up my idea that he and White are working together.
- He knows too much. Somebody will have to kill him when I am not here. could do it but I'm not sure... it's too risky! - I'm guessing White and Rodriguez somehow found dirt on him and have been telling Johnson about it, if he's not the one who employed them to begin with. This further backs up my idea that McCrary hired somebody to kill Johnson.
- I'm sure that Cheapskate would kill somebody if that was profitable. Interesting... - Not sure who this could be. I don't think this is a hint to who the murderer is as much as it's a clue that McCrary hired somebody.
- I will not let some Sugar take over my place! - Not sure who this could be. Still thinking about it.
Edit: Might refer to White? Sugar is usually white. Could mean that Sophia is spying on him because she's waiting for him to screw up so she can take his place as head honcho.
- Mr. Vampire. Always hiding. Always watching. Always ready to act! - Still thinking about this one, but it could be one of the people spying on him. "Mr." implies that it's not White, so could be Rodriguez. The vampire thing might refer to him chewing all the time, but I'm not certain about this. I have a feeling that the names probably relate to some famous vampire or somebody who played a vampire, but I wouldn't know.
- I'm not sure if I've ever seen somebody washing his hands as carefully as Non-Kevin does. Amusing. - Some other reference I probably don't get. Must be some famous person whose first name is Kevin and last name is the same as one of the suspects. I'll get back to this after a bit of Google searching.
Edit: Kevin Spacey. So it refers to Roy.

Thanks for picking this up, zeo.
I agree it looks like they (Sophia and Miguel) could be in it together and she hired him to get rid of victim but I am not sure how to prove it (somethign with the bubble-gums perhaps?) and if ti is correct at all.

This guess is pretty out there, but it's possible that Roy's excessive hand washing has something to due with the missing gum, i.e. he stuck his hand in a wad of chewed-up gum and is desperately trying to wash it off. Not sure how it's related, even if it's right, however.

I went through this puzzle once again and I have a good news and a bad news. The good news is I refreshed my memory and I can assure I understand every hint of that puzzle yet again. The bad news, however, is that I realized that difficulty of this particular puzzle is at least partially artificial. The problem is I’m not a native English speaker and thus I make a lot of grammatical errors and misspellings. Maybe they are not that bad, I guess you can still understand me easily enough but it this case it’s an obstacle: as you can see there are a lot of word plays here. Every time you see some misspelling you probably assume it’s just my mistake. But in some cases I made them on purpose!!! And by analyzing those errors you can solve the puzzle. So here is my idea: if you want you can me question like this: "In sentence X you made a mistake Y. Should this sentence rather look like Z or was it on purpose?" and then I will give you a simple answer to that. It only applies to personal notes of McCrary.

I will once again repeat one of the old hints: every single line from McCrary notes contains at least one nickname. Not that it only refers to somebody. It does contain a nickname!

Is "them" in the "son of an Andrew" clue referring to one person, or multiple people?

Word "them" was used on purpose.

This line is correct too? This one too?

It's my mistake.

This, however, is not. It's on purpose.

....what, am I the only one working on this anymore?
Well, whatever. Guess it's up to me to solve it.
My theory at the moment is pretty wild, but here goes:

All of the security guards were suspicious of each other and each trying to be the spy. Jacob, after hearing McCrary ask if he killed a man, began lurking in the dark, being a "vampire" by trying to remain hidden while monitoring the activities of others. Roy was worried from the beginning since he thought the complex was too big for three guards, so he hid in the bathroom to listen to who went by. Miguel, either strategically or on accident, placed his gum in some location where somebody could step on it or otherwise get it stuck to them. I mean, nobody just LOSES the gum they were chewing that easily.
Sophia, on the other hand, knew what McCrary was up to and decided she could profit by joining him and moving up in her position somehow. She was hired by him to kill Johnson. It's possible that McCrary wanted her to get caught and for Ward to kill her, but that's a bit irrelevant. It's possible that Miguel saw her step or otherwise touch his planted gum or saw the gum on her, and took that as the signal that she'd been somewhere she hadn't. He apparently doesn't want to believe she did it despite this evidence, seeing as he defends her and has a crush on her. However, when he saw her headed to the bathroom, he made sure she didn't go in that direction because he knew that she'd go in there to wash it off. Either that, or he didn't want her to see that Roy was listening in on her. Roy then came over to help Miguel after hearing him quarrel with Sophia, and realized that she might overpower him with her strength and get rid of the evidence. After that, Jacob came over to break it up.

Of course, this is assuming that Miguel lost his gum on purpose. If it was on ACCIDENT, well, that's a whole different theory.

.....am I at least close?
Is anybody else here in this thread but me?
It's lonely in here, and the last guy who was lonely in this place got stabbed and ended up in a glass container...