Case Details:Kevin Duane Marshall, 38, of Eagle Butte, South Dakota, was reported missing after he disappeared on or about May 19, 2016. Marshall, who lived in a family-owned trailer on the outskirts of Eagle Butte on the Cheyenne River Reservation, was last seen at his mother's residence in Eagle Butte on that date. He was planning to travel to Rapid City, South Dakota, to attend his oldest daughter's graduation ceremony from Central High School, scheduled for that week, but he never arrived and has not been heard from since. He was last seen wearing a t-shirt and black jeans. Family members have said an argument between Marshall and his girlfriend at the time occurred close to the point of his disappearance, and that Marshall had a history of drug and alcohol addiction; the exact circumstances of his disappearance remain unclear.

The case is investigated by the Cheyenne River Sioux Tribal Police Department. Marshall's case is listed with the South Dakota Missing Persons Clearinghouse and with NamUs. Family members have stated that search efforts have been limited primarily to relatives traveling between Eagle Butte and Rapid City, and that a formal search party convened only once, on short notice, in the period after his disappearance. No suspect or person of interest has been publicly named, and no arrests have been made. Marshall's case has been cited in tribal and regional reporting as one of several unresolved missing-person cases from the Cheyenne River Sioux Tribe, amid broader concern over missing and murdered Indigenous people in the region. As of this writing, Marshall remains classified as an endangered missing person and his case remains open.