Authorities have arrested a man in the brutal murders of an Alabama mother, her pregnant teenage daughter and 12-year-old son, who were found bound in their home April 20. Mobile County Sheriff Paul Burch said William Graham Oliver, 54, was charged with eight counts of capital murder, according to a  report  from local outlet WALA. He was booked into jail Tuesday. Fox News Digital previously reported Mobile County Sheriff’s Office deputies responded to a home in Wilmer, Alabama, just after 2:30 a.m. April 20, where they found three bodies in separate rooms with their hands tied behind their backs . The victims were identified as Lisa Gail Fields, 46, who was stabbed; Keziah Arionna Luker, 17, who was shot; and Thomas Cordelle Jr., 12, who had his throat cut and was nearly decapitated. William Graham Oliver was charged with eight counts of capital murder after the killings of a mother, her pregnant teen daughter and 12-year-old son.…