Federal prosecutors say two Michigan hunters, sentenced Monday after guilty pleas in a 2009 Arctic National Wildlife Refuge grizzly bear hunt, are the latest from an investigation of the firm that guided them.

According to U.S. Attorney Karen Loeffler’s office, 40-year-old Mark A. Peyerk and his mother, 66-year-old Charlotte M. Peyerk, were sentenced Monday in Fairbanks by Magistrate Judge Scott A. Oravec. The two pleaded guilty in September to conspiring to violate federal wildlife laws, taking a grizzly bear out of season in ANWR, and making a false record of wildlife shipped interstate.

Assistant U.S. Attorney Stephen Cooper says the Peyerks and their guides agreed to illegally shoot the bear on the day before hunting season’s opening day. At their sentencing, Oravec noted aggravating circumstances surrounding their deliberate cover-up of the illegal kill.

“The Peyerks’ cameras had the date indicator altered to make it appear the bear was killed on opening day,” prosecutors wrote. “They also falsified the date of kill on a State of Alaska record and on a Safari Club International trophy entry form. Believing the false statements, Safari Club International awarded Charlotte Peyerk the ‘Diana Award’ for ‘ethics in hunting.’”

Cooper says the case dates back to a visit several seasons ago by U.S. Fish and Wildlife Service agents to an ANWR camp operated by Fair Chase Hunts.

“They found a few violations, and one thing just led to another,” Cooper said.

The subsequent investigation has led to almost a dozen arrests of Fair Chase Hunts participants, most of whom Cooper describes as “assistant guides, packers, an occasional hunter.”

The two major cases, however, were made against the firm’s operators, including master guide Joe Hendricks. Hendricks pleaded guilty last year to 13 federal counts, including conducting a commercial enterprise on a wildlife refuge without a special use permit.

“He was the head of the whole thing, pretty much,” Cooper said. “He was one of the few master guides in Alaska history.”

Registered guide Christopher Cassidy, Fair Chase Hunts’ other operator, apparently became involved with the company because he had a hunting plot in ANWR adjacent to Hendricks’. He pleaded guilty in 2011 to 16 counts, including wanton waste of game and the sale of unlawfully taken and possessed wildlife.

“He was a partner and involved in a plan to ultimately buy out Hendricks,” Cooper said.

At Monday’s sentencing, each of the Peyerks was fined $20,000, with the two also ordered to make a total of $15,000 in community service payments to the National Fish and Wildlife Foundation. The Peyerks also forfeited the bear and hunting rifle from the incident, as well as their hunting privileges during Mark Peyerk’s five years of probation and Charlotte Peyerk’s four years.

Oravec also ordered the Peyerks to write letters of apology to Safari Club International for fraudulently submitting the bear kill for the Diana Award, which Charlotte Peyerk must offer to return.