A 70-year-old Idaho Falls man died Wednesday afternoon after he had a sudden major medical event and drove his truck into the Blackfoot Reservoir, according to the Caribou County Sheriff’s Office.

Daniel Lee Boring was pronounced dead at the scene following the medical emergency, which was reported to police by witnesses at 12:49 p.m.

According to the Sheriff’s Office, his truck drove at a high rate of speed off of an 8-foot embankment into the reservoir. Sportsman at the scene told authorities they had witnessed him coming out of the reservoir and loading his boat onto a trailer before driving away.

“The truck became mired in the mud and was in about 2 feet of water,” the Sheriff’s Office said in a press release. “The sportsmen rushed to the location to render aid and found Daniel was not responsive and called 911 for help.”