A 77-year-old man died Wednesday in Grant County after driving his hovercraft vessel off of the frozen waters of the Mississippi River and into a tree, the Sheriff's Office said.
The Grant County Sheriff's Office said it believes Gary Kaiser, of Potosi, had a medical event shortly after leaving shore in his hovercraft near Jay's Landing in the town of Bloomington around 8:30 a.m.
Kaiser hit a tree on an island about 100 yards away from shore, the Sheriff's Office said. He died on scene.
The Sheriff's Office said the crash is under investigation.
The Bagley Fire Department, Bagley First Responders, Bloomington Fire Department, West Grant EMS, Wisconsin DNR and the U.S. Fish and Wildlife Service assisted at the scene.
Photos: Looking back at deadly 100-car pileup on foggy interstate in 2008

Emergency vehicles, cars and people fill I-90 after multiple car accidents on I-90 East and West bound lanes near Madison due to dense fog, Sunday, January 6, 2008 near Madison, Wis.

A State Patrol Officer speaks to people next to their vehicle that turned over in an accident on the west bond lane of I-90, Sunday, January 6, 2008 in Madison, Wis. Multiple cars and trucks in different sections of I-90 East and West lanes collided due to dense fog.

A tire rests in the I-90 East bound lane after a multiple car accident due to heavy fog, Sunday, January 6, 2008 in Madison, Wis.

People stand around on I-90 in dense fog after multiple accidents on I-90 East and West bound lanes shut down traffic, Sunday, January 6, 2008 in Madison, Wis.

A car sits near a semi-truck after multiple car accidents on I-90 East and West bound lanes near Madison due to heavy fog, Sunday, January 6, 2008 in near Madison, Wis.

Carrie Raymond suffered a mild concussion and was carried off to an ambulance after multiple car accidents on I-90 East and West bound lanes near Madison during dense fog , Sunday, January 6, 2008 in Madison, Wis.

A person is assited by emergency personnel after multiple car accidents on I-90 East and West bound lanes near Madison due to dense fog, Sunday, January 6, 2008 in Madison, Wis.

A State Patrol officer walks off of the Madison city bus provided for people who after multiple car accidents on I-90 East and West bound lanes near Madison due to dense fog, Sunday, January 6, 2008 in Madison, Wis.

Rescue workers help a women hurt in a multiple car accident on I-90 in the west bound that occured during dense fog , Sunday, January 6, 2008 in Madison, Wis.

A firefighter walks down I-90 east bound after multiple car accidents on I-90 East and West bound lanes near Madison due to heavy fog, Sunday, January 6, 2008 in Madison, Wis.

One man, left talks on a cell phone as a nothing looks a damage on a car after multiple car accidents on I-90 East and West bound lanes near Madison due to dense fog, Sunday, January 6, 2008 in Madison, Wis.

State Trooper L.C. Block, center right, holds the hands of Carter Raymond far right and his cousin Kyle Czarnik as Kyle's mother Andrea Thorngren holds her sons hand and walk away from the Multiple car accidents on I-90 East and West bound lanes near Madison in dense fog , Sunday, January 6, 2008 in Madison, Wis.

A State Patrol Officer walks pass a semi-truck involved in a multiple car accident due to dense fog on I-90 East bound near Madison, Sunday, January 6, 2008 in Madison, Wis.

State Patrol officers survey the damage on a vehicle after multiple car accidents on I-90 East and West bound lanes near Madison due to heavy fog, Sunday, January 6, 2008 in Madison, Wis.

R.J. Callaway, back to camera, helps people onto a Madison city bus to get out of the cold after multiple car accidents on I-90 East and West bound lanes near Madison due to heavy fog, Sunday, January 6, 2008 in Madison, Wis.