GILLETE, Wyo. - No charges have been filed against a South Dakota man and his sons in the death of a co-worker, who was found dead after an altercation.

Forty-nine-year-old Curtis Buchholz Sr. of Loomis, S.D., 26-year-old Curtis Buchholz Jr. of Mitchell, S.D., and 24-year-old Michael Buchholz of Deadwood, S.D., were released from a Gillete jail on Friday.

They had been held overnight on suspicion of involuntary manslaughter in the death of 44-year-old Peter Nels Huke of Mitchell, S.D. But, an autopsy later showed Huke died of a heart attack.

Police say the four men were involved in an alcohol-fueled altercation on Wednesday night. Huke was found dead Thursday morning.

The four men were in Gillete for a heating-and-ventilation project.