FAIRPLAY, Colo. -- Park County Sheriff Fred Wegener said the more than 30 bison slaughtered last week were the result of a civil dispute between two neighboring ranchers.

Wegener said he "probably" will recommend charges in the case and that the Park County district attorney's office will begin handling the matter this week.

Sheriff's deputies found the carcasses of 32 bison Thursday after a 911 caller reported that someone was gunning down the animals. About a dozen hunters claimed they had permission to shoot the animals. The hunters shot the animals over a period of perhaps several days, Wegener said.

Wegener said the bison belonged to Monte Downare. The sheriff said the animals wandered off Downare's property and onto another ranch, the Hawn Ranch, and federal land.

The Hawn Ranch is near the Downares' ranch but not adjacent. It's not known if authorities have spoken with the owner and caretaker of Hawn Ranch.

Charges of aggravated cruelty to animals are being considered because of the way the carcasses were abandoned, Wegener said. Trespassing and evidence tampering charges could also be filed.

Bison are considered a domesticated species and are not covered by hunting and wildlife laws, said Tyler Baskfield, a spokesman for the Colorado Division of Wildlife.

"This is not the state's wildlife. This would not be regulated by us in any way," he said.

Dave Carter, executive director of the Denver-based National Bison Association, a bison-ranching industry group, said because the animals are not considered wildlife, no permit is required to hunt them.

"Let's put it this way, there is no season on bison," he said.

Colorado is home to 14,000 bison, Carter said.

The state Department of Agriculture also said it has no jurisdiction over what happens to bison on private or public land.