Don Blankenship, former CEO of Massey Energy, has been sentenced to 12 months in prison for conspiring to violate federal mine safety laws, becoming the first American executive to be imprisoned for breaking the nation’s safety laws.

The sentence, meted out by U.S. District Judge Irene C. Berger, includes a $250,000 fine and comes six years and one day after Massey’s Upper Big Branch coal mine in West Virginia exploded, killing 29 men. The explosion was the largest mining accident in four decades.

Blankenship was accused of knowingly allowing mine safety violations to continue, contributing to the ultimate tragedy.