Boogeyman

During his childhood, Tim Jensen witnesses his father be taken by the Boogeyman, an evil creature which lives in all closets worldwide. Since then, he has taken precautions to ensure that the Boogeyman cannot get to him, such as sleeping on a mattress on the floor, and removing all closets from his home, and keeping all his clothes in a dresser drawer.
After a Thanksgiving trip with Jessica (his girlfriend) to her parents' house, Tim has a premonition in which his mother tells him to return to the family home. When he phones the hospital, he discovers his mother has died. Upon returning to the psychiatric ward where he grew up after his father died, he discovers that one of the patients, a young girl, is being threatened by the Boogeyman, which lives in the ceiling of her room.
Upon a suggestion by his psychiatrist that returning to his family home to spend the night in that house would be a good idea, Tim returns to his old Victorian style house in the open country, where he relives memories of his mother telling his father that the Boogeyman does not exist and therefore cannot possibly harm Tim. Tim is briefly attacked by the Boogeyman when he enters the downstairs closet. Tim meets a young girl in his woodshed, named Franny, who wants to know if it's true that the Boogeyman murdered Tim's father. Searching the woodshed he discovers a disturbing file of Missing Person lists and documents left by Franny, and upon flicking through them, he discovers a collection of missing children whom were all taken by the Boogeyman.
Tim panics and attempts to leave but Jessica abruptly shows up takes Tim out of the house for a night in a quiet motel, where she is murdered by the Boogeyman, dragging her into the bath.
Tim returns from getting ice and preparing drinks and enters the bathroom, where he finds that Jessica is missing. He realizes what has occurred, and stumbles blindly into a closet, and then walks out into his family home, just as Kate, his friend, has returned to his home and, upon hearing noises from the closets, was about to open the door herself. Tim drags Kate back to the hotel, where they find the empty bath; this time with blood on the side. Kate begins thinking that Tim might've harmed Jessica; but Tim angrily denies it. Frustrated at Tim's refusal to tell her what is really wrong with him, Kate claims that the person Tim saw in her house was in fact her deaf father. Kate calls Tim's Uncle Mike to have him check on Tim.
Tim returns to his house and meets Franny once more, who leads him to a house full of proclamations describing the Boogeyman. There is a chair in the middle of the room facing a closet. Tim remembers this room as being the home of a doctor whom everyone thought was insane. Franny then reveals herself to be one of the kids the Boogeyman murdered and disappears, telling Tim he'd best go to the place where it all started. The Boogeyman pulls Tim through various portals in time through the closet, eventually depositing him in his childhood room, where he smashes various toys the Boogeyman uses to give itself form before eventually defeating it and being returned to the present.
With the Boogeyman gone, Tim hopes that his and Kate's lives will be safer. Morning dawns and Tim already feels better, thinking he's safe. However, a post-credits scene reveals a young girl being tormented by the monster, revealing that the Boogeyman has resurfaced out of the closet.

Question: Who murdered Tim's father?
Answer: Boogeyman