Mark William Allen was 31 when he was last seen in Livermore, California, on December 6, 2015. He is described as 6 feet 4 inches tall, about 260 pounds, with brown hair, blue eyes, facial hair that was likely ungroomed, and a noticeable scar at the base of his spine. On the day he disappeared he was reportedly wearing cargo pants and a sweatshirt.

Mark had a history of mental health struggles and often wandered at night. He had disappeared for months before and usually returned, which initially led some to treat this absence as voluntary. Before going missing he may have been living a transient lifestyle and was known to use shelters or religious facilities in Livermore and in nearby Pleasanton and Dublin.

His whereabouts remain unknown and he has not been seen or heard from since December 6, 2015. Anyone with information is asked to contact the Livermore Police Department or Cody S Investigations.

Did anyone in Livermore, Pleasanton, or Dublin see Mark around that December 2015 timeframe or know where he might have gone?