(Tacoma, WA)  --  Investigators are trying to find out what caused a fire that left a three-year-old boy dead at a duplex in Tacoma, Washington.  Officials say the boy's mother was taken to a hospital for treatment of smoke inhalation, as a result of yesterday's fire in the 64-hundred block of South Tyler.  Relatives told Q-13 the boy, Nehemiah Bonds, was napping with his mother when the apartment began to fill with smoke.  Tacoma Fire officials say it's not clear whether the apartment had a working smoke detector.