Police in Sumner County, Tennessee say a teenager bludgeoned his mother, 46-year-old Melanie Davis, to death Friday night.
Davis was an athlete, training for a triathlon with a group of friends.
Her training partners said last night they were expecting to meet her yesterday morning.
Her friends say Davis was a widow, raising her two teenage sons on her own.
It was her 16-year-old who called the police after discovering his mother's body and his house on fire.
Police arrested the 15-year-old son seven miles away after tracking his cell phone.