She used to be nice until her son, Jason drowned at Camp Crystal Lake. So, she's getting her revenge for her son's death unitl she got beheaded and died.
Pamela Voorhees was the mother of the unstoppable killing machine known as Jason Voorhees. In 1947, Pamela was a young and pregnant newlywed living in a trailer in Cadiz, Ohio with her abusive husband Elias.
Pamela believed that she could actually hear the thoughts of her unborn child instructing her towards committing acts of violence. Whether this was merely an aspect of a deep-rooted psychosis or a reflection of some supernatural manipulation is unknown.
In September of that year, after suffering another in a long series of beatings perpetuated by her husband, Pamela heeded the voice inside her that told her to "kill".
While Elias was sleeping, Pamela picked up an ax and hacked him to pieces. She discarded the remains and burned the trailer to the ground.
Without a husband or a home, Pamela felt lost adrift. She drove across the country until she reached the suburban community of Crystal Lake. She felt God had called her to this place and she purchased a home.
She got a job working as a short-fry cook at a local diner. On Friday, October 13th, Pam met David and Louise Christy. The Christys told her that they were re-opening a campground out near the lake and asked her to work for them cooking for seventy-five children over the summer season.
On the day that Pam accepted the job, she went into labor. Her son Jason was born with severe physical deformities, but a mother's love blinded Pamela who felt that he was "perfect".
In June of 1957, Pam was working at Crystal Lake when she received news about her son. Rushing home, she learned from her nanny Mrs. Cunningham that Jason had been killing and mutilating small kittens.
Rather than admonishing the boy's actions however, she instead cradled him, telling him that she will always protect him. She did decide however, that she would have to leave her job in order to keep an eye on Jason.
Dave Christy didn't want to see Pamela go, so he invited her to bring Jason to live at the campground so that she could always keep an eye on him.
Later that year, eleven-year-old Jason Voorhees drowned in Crystal Lake and the "death" of her child drove the overprotective Pamela insane.
The camp counselors charged with keeping an eye on him were off making love in the woods. Stricken with grief, Pamela took some time away from the camp.
In 1958, she begged the Christys for the chance to work at the camp again. Her motivation behind this is unclear, but it may have been sparked by the knowledge that the two negligent counselors who allowed her son to drown, Barry and Claudette, were once again working at Camp Crystal Lake.
Pamela avenged her son's death against two camp counselors whom she found copulating inside of a cabin. Pamela believed that these two reflected the sinful nature of all whose actions allowed her son to die.
In 1979, she returned to Camp Crystal Lake and killed several more counselors. She picked up a young camp counselor named Annie in her jeep and told her the story of her life before slaughtering her.
She also killed the campground manager, Steve Christy, the son of David and Louise Christy. One woman survived the massacre however - Alice Hardy. Pam and Alice fought one another on the shore of Crystal Lake and Alice beheaded Pamela with her own machete.
Jason Voorhees, still alive and living the woods nearby, witnessed his mother's death and began a bloody crusade of vengeance against anyone who dared to trespass on his territory. He collected his mother's head and placed it on a shrine in his own cabin.
When Jason was in pursuit of Ginny Field, Ginny came upon Pamela's shrine and used child psychology in a desperate gamble to save her own life.
She pulled her hair back, donned Pamela's dirty sweater and began speaking to Jason in an authoritative voice. The trick worked momentarily and Jason believed that he was seeing the image of his dead mother speaking back to him.
Years later, Freddy Krueger manifested himself as Mrs. Voorhees and appeared to Jason in Hell. She urged him to rise up and kill again, emphasizing that he needed to go to Elm Street to deal with some troublemakers.
Jason was resurrected from Hell and did as he believed his mother was instructing him to do. When Jason's rampage grew out of control, Freddy appeared as Mrs. Voorhees again in a dream, admonishing Jason as "a dog that doesn't know when to stop eating".
Freddy further antagonized Jason by making it appear as if he was holding his mother's severed head in front of him.