AMHERST, Wis. -

The Portage County coroner says a farmer was accidentally killed last month when he was exposed to hydrogen sulfide gas.

Coroner Scott Rifleman said Wednesday that 29-year-old Michael Biadasz was using a piece of farm equipment to agitate a large outdoor manure pit on his family's farm near Amherst. That opened a crust layer on top of the pit and expelled the gas.

Other workers found Biadasz when they arrived Aug. 15 to haul away manure from the large tank.

The wind was calm and the sky clear early that morning, with a heavy layer of fog near the ground. Stevens Point Journal Media reports the lack of air movement and sudden release of hydrogen sulfide gas, which is heavier than air, created a deadly dome of air.