A 21-year-old Rapid City man was killed Saturday in a mountain biking accident in the Black Hills near Rockerville.

Pennington County  Sheriff’s Sgt. Greg Foster says Curtis VanOsdel was riding down a steep hill on a U.S. Forest Service trail when he hit a rock, lost control of his bike and struck a tree.

VanOsdel, described as an experienced rider, WAS wearing a helmet, but still suffered a fatal head injury and was pronounced dead at Rapid City Regional Hospital. Sgt. Foster says it “was just a tragic accident.”