CLEAR LAKE, Iowa – An autopsy will be performed to find out what killed man on Clear Lake Saturday.

The Iowa Department of Natural Resources says Daniel Ryan LInderman, 28 of Waukee, was tubing behind a boat when he fell into the water around 2:30 pm. The boat was being operated by Timothy Heitland of Buffalo Center.

The DNR says Linderman was seen swimming back to the boat when he seemed to suffer a medical emergency and went face down in the water. He was wearing a life jacket at the time. A nearby DNR Water Patrol Officer rushed to the scene while someone from the boat tried to hold Linderman’s head above water. Linderman’s body was eventually gotten into a DNR boat and he was taken to shore.

CPR was performed and Linderman was taken to MercyOne North Iowa Medical Center, where he was pronounced dead. The exact cause of death has not yet been determined.

The Clear Lake Fire Department, Ventura Fire Department, and Mason City Fire Rescue assisted with this incident, which remains under investigation.