ELK POINT, S.D. — A college student from Iowa who is presumed drowned in the Missouri River in South Dakota was trying to help others when he went missing.

Twenty-three-year-old Tom Patterson, of Frostburg, Maryland, was swimming with friends Sunday afternoon southwest of Elk Point when he disappeared.

Union County Sheriff Dan Limoges says new information from a witness indicates Patterson was trying to help other swimmers back to shore when he was swept away by the current.

Authorities are continuing to search for a body.

Patterson had been attending classes at Briar Cliff University in Sioux City, Iowa.