ELK POINT, S.D. (AP) — 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.

READ MORE: 29-Year-Old Man Shot & Killed Overnight

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.

READ MORE: M&T Bank Stadium To Open As COVID-19 Mass Vaccination Site Today

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

Follow @CBSBaltimore on Twitter and like WJZ-TV | CBS Baltimore on Facebook

MORE NEWS: 'Game-Changing' Johnson & Johnson Single-Dose Covid-19 Vaccine Meets Requirements For Emergency Use Authorization, FDA Says

(© Copyright 2016 The Associated Press. All Rights Reserved. This material may not be published, broadcast, rewritten or redistributed.)