Raymond Johnson, 52, is scheduled to be executed by lethal injection in Oklahoma on Thursday, nearly two decades after he was convicted of the brutal murders of his ex-girlfriend and her 7-month-old daughter. Johnson is set to receive the lethal injection at the Oklahoma State Penitentiary for the June 2007 deaths of 24-year-old Brooke Whitaker and her infant, Kya. Prosecutors detailed how, following an early morning argument at Whitaker’s Tulsa home, Johnson repeatedly struck her head with a metal claw hammer, fracturing her skull and causing over 20 lacerations. Despite her severe injuries, Whitaker remained conscious and pleaded with Johnson to spare her and Kya, who was asleep in a bedroom, according to documents prepared for Johnson’s clemency hearing. "She begged him to call 911. She begged him to let her mom come get baby Kya. She begged him to think of her children," the Oklahoma Attorney General’s Office stated.…