Authorities in Tennessee have arrested an Iowa man on suspicion of murder after his parents and niece were found dead in Nebraska this week. According to the Omaha World-Herald, 18-year-old Leonna Dalton-Phillip and her grandparents, John Dalton Sr., 70, and Jean Dalton, 65, were shot and killed around 7:30 p.m. Tuesday. Dalton-Phillip had just arrived …