Silent Hill

Rose and her husband, Christopher Da Silva, are concerned about their adopted daughter, 9-year old Sharon, who has been sleepwalking while calling the name of a town, "Silent Hill". Desperate for answers, Rose takes Sharon to Silent Hill. As they approach the town, she is pursued by police officer Cybil Bennett, who has become suspicious of Rose's motives after witnessing Sharon panic at a gas station when her drawings are mysteriously vandalized. A mysterious child appears in the road, causing Rose to swerve and crash the car, knocking herself unconscious. When she awakens, Sharon is missing, while fog and falling ash blanket the town.
Rose wanders the empty streets of Silent Hill looking for her daughter but is stopped when, upon the sound of a siren, the town transforms into a dark and distorted alternate version of itself, and she encounters a large group of disfigured monsters, including the Janitor in a school bathroom after digging out a piece of wood from the fog world's janitor's mouth. When the town reverts to its normal state, she meets a woman named Dahlia Gillespie, who speaks of her own daughter, Alessa, being abused by the townspeople. Upon seeing a photo of Sharon in Rose's locket, Dahlia mistakes Sharon for Alessa, and tries to steal the necklace from Rose. Rose returns to her car and runs into Cybil, who arrests her. As they head back to the road out of the city, they discover that the road is cut by a huge fracture. The two women eventually pair up to search for Sharon, experiencing Silent Hill's surreal dark side together and barely escape a tall sword-wielding figure called Pyramid Head.
Meanwhile, Christopher also simultaneously scours the town, shown to be abandoned and without mist and falling ash as it is to Rose and Cybil, with the assistance of officer Thomas Gucci, who is there in search of the missing Cybil. Christopher discovers documents revealing that the town was abandoned after a coal seam fire thirty years ago, along with a photograph of Dahlia's daughter, who is identical to Sharon. Told to stop investigating under threat of incarceration, he returns home.
Rose and Cybil meet Anna, a woman who leads them to a local church for refuge when the alternate version of the town, referred to by Anna as "the darkness", returns. As they approach it, Anna is killed by Pyramid Head after he completely excoriates her with his bare hands. In the church, Rose and Cybil discover a cult headed by a woman named Christabella. Christabella tells Rose about a "demon" who knows Sharon's whereabouts. After convincing Christabella to help them locate the "demon", Rose and Cybil are taken to a local hospital. There, Christabella also sees the photo of Sharon in Rose's locket and, seeing the likeness between Sharon and Alessa, condemns Rose and Cybil as witches. Cybil is captured by the townspeople while Rose descends into the hospital basement. There, Rose encounters a burned Alessa on a bed and Dark Alessa, the incarnation of the darkness in Alessa's soul.[6]
In a flashback, Rose discovers that Silent Hill had a long history of witch-burnings, stemming from the cult's beliefs. Thirty years before Rose's arrival, Alessa was stigmatized for having been born out of wedlock by an unknown father; her schoolmates bullied her, and she was sexually assaulted by a janitor, named Colin, while hiding in a bathroom from her classmates. Christabella declared her filth, and Dahlia agreed to Christabella's suggestion that she allow the cult to "restore innocence" in Alessa. When not allowed to follow Alessa into the ritual, Dahlia realized that they intended to kill her daughter and ran to the police.
Alessa was ritually burned, but in the midst of the ritual, the device holding her above the fire pit broke on one side, causing it to swing and knock over the pit, setting the church ablaze and starting the conflagration that destroyed Silent Hill. When Dahlia returned with the police, Alessa was found with third degree burns, but still alive. While in the hospital, Alessa's pain and rage caused her dark side to become incarnate in the form of a duplicate of herself; a manifestation of the darkness in her soul. Rose then learns that Sharon is the manifestation of the goodness in Alessa's soul. After the flashback, Rose is told that she must aid Alessa in her revenge by granting her entry into the church, and that Christabella will soon find Sharon and attempt to burn her as well. She decides to help, and allow Dark Alessa to merge with her body.
Rose enters the church after Cybil has just been burned alive by the townspeople, and Sharon is about to suffer a similar fate. She confronts Christabella with her knowledge of the truth, attempting to convince the cult that they are in denial of their own fate. Christabella stabs Rose, causing her blood to drip onto the church floor. The blood serves as a vessel through which Alessa exits Rose and brings the "darkness" into the church. Alessa attacks the cultists with long strands of barbed wire, which she then uses to violate and eventually bisect Christabella, killing her. The townspeople are also killed, leaving Dahlia, Rose, and Sharon the only survivors. At the end of the massacre, Alessa and Sharon fuse and become one person again.[7]
As they leave the town, Rose discovers that the abyss and the fracture is gone, allowing them to leave Silent Hill, while Dahlia stays behind. Meanwhile, Christopher returns home and falls asleep on the couch. He wakes up just as Rose and Sharon/Alessa return home, but they arrive in the foggy, Silent Hill version of the home, while Christopher sees rain and sunshine, indicating that Rose and Sharon/Alessa are still in an alternate reality.

Question: Who sexually assaulted Alessa?
Answer: Colin