Yellowstone National Park staff killed a baby bison when the newborn calf was rejected by its herd after a man "intentionally disturbed" the calf in the northeast corner of the park, authorities said.
The unidentified man approached the calf in the Lamar Valley area of the park, where the newborn had been separated from its mother when the herd crossed the Lamar River, the national park said in a press release.
The man pushed the calf, which was struggling to cross the river, up from the river and into the roadway, the park said. Park visitors later observed the calf walking up to cars and following people and vehicles.
"In this case, park rangers tried repeatedly to reunite the calf with the herd," park officials said. "These efforts failed," they added, noting that interference from humans can cause wildlife to reject their babies.
Park staff later killed the calf because it was abandoned by the herd and was causing a "hazardous situation by approaching cars and people along the roadway."
"Approaching wild animals can drastically affect their well-being and, in this case, their survival," the park said.
Park regulations require visitors to stay at least 25 yards away from all wildlife, including bison, and at least 100 yards away from bears and wolves. Fines, injuries and even death can occur if people disregard the regulations, the park said.
Authorities are asking the public for information about the incident involving the man, whom they described only as a white male in his 40s to 50s wearing a blue shirt and black pants.
The park said the incident is under investigation, though it is unclear if the man could face criminal charges. A spokesperson for the park did not immediately respond to a request for comment from NBC News.