GREAT FALLS, Mont. (AP) — Search crews in Montana on Tuesday found the body of a 17-year-old Nebraska boy who witnesses said had been trying to swim across the Missouri River.

The Cascade County Sheriff’s Office said search crews were called to an area along the river near the town of Cascade after the boy was reported missing Monday evening.

His body was found Tuesday morning by sheriff’s office employees using footage from an aerial drone that was deployed to help with the search.

The victim was identified as David Van Essen of Greenwood, Nebraska.

Witnesses told investigators that Van Essen attempted to swim across the river without wearing a lifejacket. He was seen going under the water and did not resurface.