Police have arrested a 23-year-old man suspected in the slaying of his grandmother who was found decapitated at a home in Santa Rosa. Police say officers responding to reports of a possible homicide discovered the 64-year-old woman dead last Thursday. Officials say the woman’s head was not at the residence. The suspect was arrested Saturday morning in San Francisco. The victim’s head was found Saturday evening near a creek. Officials say the suspect had recently been released from prison after being incarcerated for assault with a deadly weapon.