Heather Stephenson-Snell was a professional psychotherapist and leader of an all-female biker gang who became obsessed with revenge after her former partner, Adrian Sinclair, ended their relationship to be with another woman, Diane Lomax. Following an 18-month campaign of harassment, she drove from York to Radcliffe on Halloween night in 2003 disguised in a "Scream" mask and ghostly white sheet, carrying a sawn-off shotgun with the intent to kill her rival. When her knocking at Lomax's door disturbed the neighborhood, a 43-year-old neighbor named Robert Wilkie confronted her and attempted to remove her mask; Stephenson-Snell shot him at point-blank range, killing him almost instantly.