CONSHOHOCKEN, PA - December 10, 2007 --The man accused of sexually assaulting and killing his mistress' 14-year-old daughter confessed to the crime after his arraignment while cameras were rolling.Ebony Dorsey's body was found Sunday in a plastic container behind a home on Union Meeting Road in Whitpain Township. Tonight police have charged 48-year-old Mark O'Donnell with her death. O'Donnell freely admits he killed 14-year-old Ebony Dorsey. He talked about it as he came and went from district court in Conshohocken. O'Donnell told reporters, "I caught her molesting my daughter. You would have did the same thing." But that's not what he told police. O'Donnell was the last person seen with Ebony before she disappeared. O'Donnell is her mother's boyfriend. He took her to his Plymouth Meeting apartment Thursday night to baby-sit his 4-year-old daughter. Her mother reported her missing when she didn't come home from school Friday. It turns out she never got there. O'Donnell now admits he killed her. "She had been beaten about her head and face. She died of asphyxiation, she had been strangled, we believe manually as well as her pajama bottoms being wrapped around her neck," said Risa Ferman, the Asstistant District Attorney of Montgomery County. The autopsy shows she had also been sexually assaulted. Police found Ebony's body at O'Donnell's nephew's house yesterday. He had allegedly stuffed her into a blue storage box and covered it with leaves. O'Donnell was later found hiding at another relative's house in Upper Gwynedd. It appears ebony was living in a troubled home with her mother in Ambler. Her mother, Danielle Cattie told police that before Ebony left with O'Donnell he had been smoking crack cocaine for hours. She also admits that she's a heavy user of cocaine. Despite the odds, Ebony was an honors student at Wissahickon High School. Her classmates shared hugs and tears today. Her classmates described her as happy and cheerful, always there to make others smile. Tragically, Ebony's smile will never be seen again. O'Donnell faces multiple charges including first-degree murder, which could carry the death penalty. This is also an ongoing investigation that could lead to charges against Ebony's mother.