A rare white female wolf that hikers found as she lay dying last month on the north side of Yellowstone National Park near the Montana border, was shot illegally, officials have determined.

The wolf had to be euthanized by park officials because of the severity of her wound.

She was the only white wolf living in the park, though there had been two others before her. She was 12 years old when she was killed, twice the average age of wolves in Yellowstone.

She was the alpha female of the Canyon Pack, one of 10 packs in the park, and she had paired with the alpha male for nine years. Over that period, biologists say, she whelped 20 pups, 14 of which lived to be adults.

After she was euthanized, the white wolf’s carcass was sent to the United States Fish and Wildlife Service forensics lab, and the preliminary results of the necropsy were released on Friday. Park officials are treating the shooting as a crime.