A Feather Alert was issued Monday for Samuel Sierra, a missing 36-year-old at-risk man in Mendocino and Alameda counties. Affiliated with the Round Valley Indian Tribe, Sierra was last seen in Ukiah at South State Street and Observatory Avenue. He is 5’7″, 140 pounds, with black hair and brown eyes, with tattoos on his head and forehead. Anyone who has seen Sierra is asked to contact 911 with any information.