RANCHO CUCAMONGA, Calif. -- A mother is believed to have killed her 4-year-old son and herself at a Rancho Cucamonga apartment complex.Authorities received a call around 11:34 a.m. in the 10400 block of Arrow Route regarding a dead person inside a unit. Employees at the complex had received complaints of a foul smell coming from inside the home, and when they entered they found a dead boy.San Bernardino County sheriff's deputies arrived at the scene and confirmed a 4-year-old child was dead. Deputies also found a dead woman inside the apartment.During the investigation, deputies came to believe that the 29-year-old mother killed her son and then killed herself.Authorities did not provide further details, and the investigation was ongoing.Anyone with more information were urged to call Detective James Williams at (909) 387-3598. Those wishing to remain anonymous may call the We-Tip Hotline at (800) 782-7463.