On the morning of July 17, a bison charged and gored a 47-year-old woman from Phoenix, Arizona near the shore of Lake Yellowstone in Yellowstone National Park. According to a National Park Service (NPS) press release issued yesterday, the woman was walking through a field with one other individual when the attack occurred. She was transported by air to the East Idaho Regional Medical Center for treatment.

“The woman sustained significant injuries to her chest and abdomen,” the release states. “It is unknown how close the individuals were to the bison when it charged.” The incident remains under investigation, and the woman’s condition has not been shared at this time.

The bison gored the woman in a part of Yellowstone known as Lake Village. It’s common for bison to migrate to this area en masse this time of year while the rut is in full swing. Yellowstone bison tend to rut from mid-July to mid-August.

Bison can become agitated more quickly when they’re rutting, NPS warns, making it extremely important to exercise caution around the large animals—which can reach weights in excess of 2,200 pounds and turn on a dime at speeds up to 35 miles per hour. When disturbed, they’ve even been known to ram the sides of trucks, cars, and motorcycles.

Last June, an Ohio woman was gored and tossed 10 feet into the air when she approached to within 10 feet of a bison in the Black Sand Basin area just north of Old Faithful. That woman was also transported to the East Idaho Regional Medical Facility where she was treated for puncture wounds and other injuries.

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NPS officials recommend that all Yellowstone visitors remain more than 25 yards away from large animals like bison, elk, moose, deer, and bighorn sheep at all times, and at least 100 yards away from bears and wolves. “Bison have injured more people in the park than any other animal,” the agency said. “They are unpredictable.”