Tim

History:

While the exact nature of Tim's connection with the Operator is still unclear, it is one that stretches back to his childhood. The medical records found by Jay reveal Tim's hospitalisation when he was in the second grade, exhibiting symptoms including seizures, frequent headaches, insomnia, and was judged to be a suicide risk. Along with the fact that Tim grew up in the Rosswood area (where Jay's investigations are centering around), nothing else is known about Tim's past until the shooting of Alex's student film, Marble Hornets, three years ago.

Tim only got involved in the production as a favour to Brian, the main actor in the film; he didn't know Alex prior to shooting. When Jay later questions Tim about the film shooting, he doesn't remember it all that well; Jay also exhibits memory loss of much of the events of filming, but how much Tim does remember and hasn't divulged to Jay is unclear. During filming, Tim shot behind-the-scenes style footage on a camera borrowed from Alex, and took Alex location scouting to locations including the abandoned hospital near Rosswood, where Alex attacks Tim.

Three years later, Tim has moved back to the Rosswood area, and is trying to hold down a normal life. Most of his time is taken up with his job (we haven't yet found out what he does for a living), as well as regular doctors appointments at a mental health clinic.

When Jay finds Tim living in the area, he is already aware of Tim's alter ego. The masked man (or 'masky' as he is referred to by the fanbase) who has often appeared at the scene of Jay's investigations, was uncovered by Alex and Jay to be Tim during the seven months that are missing from Jay's memory. Masky has alternately tried to attack Jay, such as when Jay goes to the house in entry 18, or assist him, such as when he saved Jay and Jessica from being shot by Alex in entry 52. Masky walks with a limp, due to Alex breaking his leg in entry 35, although Tim does not walk with a limp. Tim later admits that he has started having gaps in his memory and wakes up in random places (such as on the night that his leg was broken), suggesting that Masky is a completely different personality to Tim, and Tim has no control over or memory of what Masky does.

Tim doesn't seem to remember Jay at all when he first finds him outside his doctors office, although he does give him the behind-the-scenes tapes he filmed while shooting Marble Hornets. He also agrees to take Jay to the abandoned buildings that he went to with Alex. Tim is very hesitant about taking Jay to the abandoned hospital. While he claims not to remember taking Alex there, when they leave he says to Jay that he's "had enough of that place for a lifetime," implying either that he does remember or that he's had other incidents there in the past. When Jay chases the hooded man to the entrance to the maintenance tunnel, Tim decides he's had enough and the two of them leave.

A few days later, Tim calls Jay and asks to meet him. Jay intends on coming clean with Tim about what he's really up to, but when he arrives Tim punches him in the face before telling him that he searched online for Marble Hornets and found the videos that Jay had uploaded. Angry at being lied to and at having his privacy invaded in that way, Tim tells Jay to stay out of his life and drives off. Later, when he returns to the maintenance tunnel, Jay finds records of Tim's hospital admission during his childhood.

A short while after this, the hooded man breaks into Tim's house, steals his anti-convulsant pills, and films him having a seizure. After this, Tim breaks down in tears before walking away out of his house. When this video is uploaded to Jay's channel, Jay goes to Rosswood Park in search of Tim, but finds Masky instead, who attacks him. The next morning Jay wakes up in a shed in Rosswood, and finds Tim lying outside nearby, mask nowhere in sight. A few weeks later, Tim calls Jay asking to meet, and agrees to help him, wanting all of this out of his life again. They go back to Rosswood Park, searching the warehouse where Alex tried to shoot Jay and Jessica before heading to the tunnel. Jay receives a phonecall from Alex (who up to this point they haven't been sure whether he's alive or dead), telling them to "Leave. Now.", but while they discuss whether to stay or go, the Operator appears at the end of the tunnel. Tim has a coughing fit and is unable to move, telling Jay to run as the Operator closes in on him. Later, as Jay returns to his car, he sees Tim behind the wheel of his own car. Tim stares at Jay blankly before driving off.

The Entries
Comprehensive Timeline
Tim's page at the MH wiki
Another wiki page on Tim

Personality:

At first glance, Tim looks like just a regular guy. And that's all he's ever wanted to be, really. However, having suffered from the side effects of the Operator since his childhood, Tim's never been able to enjoy the safety of a normal life. Indeed, his life so far has been bleak and lonely. It's easy to tell this just from looking at his medical records from his hospital admission during the second grade: Tim spent a good deal of his childhood afraid, at points suicidal, and being told that everything that was happening to him was in his head, and that there was something wrong with him rather than actually being able to fight the thing that was stalking him.

Unsurprisingly the boxes on the medical form for "hobbies" and "engaging in activities" with boys of his own age are both left unchecked; it's impossible at this age for Tim to engage with any of the fun aspects of childhood. It's clear that moving away to college is something of a fresh start for him, but despite Tim's interest in learning to play various musical instruments, as well as his participation in the shooting of Marble Hornets, he's still a little awkward and reserved. In fact, if there's one word that describes Tim perfectly, it's dour, and even in college this is the impression that the tapes give of him. In fairness, we only ever see Tim at this point when interacting with Alex, and by Tim's own admission, he found Alex overbearing and difficult to work with, and it's possible that before the shooting of Marble Hornets he was happier and more open; he and Brian seem to have been good friends, after all. But the image of Tim that is portrayed both from his college years and present day is of someone who is quite closed up, gloomy, and sarcastic, all of which are probably defense mechanisms.

When Jay finds Tim in present day, he's moved back to the Rosswood area, for reasons that are unclear; given his childhood trauma there, it doesn't make much sense for him to want to return there. But it's possible that Tim was wanting the opportunity for a fresh start there, to be able to wash away his past and take control of his life. His daily life consists of his job and his frequent doctors' appointments: Tim sees the unexplained aspects of his life as something to be eradicated, rather than solved and explained like Jay does. He is still shown to be quite a private, serious, person, although again, we mostly see him through the perspective of Jay's tapes, and it's possible that he is more guarded around Jay, suddenly appearing and asking all sorts of questions. But it is very probable that Tim is determined to go it alone, both because he doesn't want to drag anyone else into the mess that is his life, but also because he is sensitive about his time spent in institutions and doesn't want people prying into it and bringing out that old pain. It's no surprise, then, that he feels completely violated when he discovers Jay's true intentions in prying into the filming of Marble Hornets: not only has he been lied to, but extremely personal details about his past have been made public for the whole internet to judge him on. While Tim does feel a sense of relief in knowing once and for all that he's not crazy, that this isn't all in his head as he's been told repeatedly his entire life, he is still only helping Jay begrudgingly, wanting him, and the Operator, out of his life once and for all. While Jay wants answers, Tim would quite happily wave a magic wand and have all of this out of his life once and for all, replaced by the normal life that he's worked to get, but which is now slipping out of his grasp once again.