Officials at Yellowstone National Park said Monday that they had to euthanize a baby calf because it was rejected by its herd.

Last week, tourists loaded it into their SUV at the national park because they were concerned for its welfare. The newborn calf was taken to a park facility by the tourists, but rangers weren't able to reunite it with its herd. The animal was later euthanized because it kept approaching people and cars along the road.

Rangers ticketed a father and son Monday, according to EastIdahoNews.com.

The pair believed the calf was in danger of freezing to death, a witness told the news website.

"They sincerely thought they were doing a service and helping that calf by trying to save it from the cold," Rob Heusevelet told EastIdahoNews.com. Heusevelet spotted the pair while visiting the park with his child, who was on a field trip with a group of fifth-graders from Idaho.

Visitors are not allowed to get near animals at Yellowstone. According to the National Park Service, visitors are required to stay at least 25 yards away from bison and other large animals.

"Every year, visitors are gored and some have been killed," the Parks Service warned. "Bison can sprint three times faster than humans can run. They are unpredictable and dangerous."

The Associated Press contributed to this report.