A pack of wolves killed 19 elk in western Wyoming, according to state wildlife officials describing the slaughter as an extremely rare “surplus kill.”

John Lund of the Wyoming Game and Fish Department said it is not unusual for wolves to kill one or two elk a night in that part of the state but to have 19 killed in one night is rare.

“It’s rare at this magnitude,” Lund told FoxNews.com. “We’ve documented it before but have not documented it to that extreme.”

A surplus killing is when an animal kills more of its prey than it can eat and abandons what's left, KGW-TV reported.

Online news outlet County 10 reported the wolves killed 17 elk calves and two adult cows at a feedground near the tiny town of Bondurant, the station reported.

Officials made the discovery Thursday morning.

Lund said the culprits may be a pack of nine wolves known as the Rim Pack.

He said there is nothing the state can do about the wolves. The animals are protected under the federal Endangered Species Act.

“We can’t take any action proactively,” Lund told FoxNews. “It’s frustrating for state wildlife management.”