An elk was euthanized in Great Smoky Mountains National Park after a YouTube video of the animal head-butting a photographer went viral, garnering more than 1.8 million views. According to WBIR in Knoxville, Tenn., when park rangers got wind of the young bull’s scuffle with the park visitor, they decided to euthanize the elk Friday, citing its history of “aggressive behavior.”

Public outcry grew after the news broke. Park officials responded to the criticism they were receiving for euthanizing the animal in a statement on the park’s blog.   

“By initiating physical contact with a visitor, the elk displayed an unacceptable risk to human safety,” Great Smoky Mountains National Park officials said. “After becoming food-conditioned, the elk did not respond to any attempts to keep it out of the area and away from humans. When wildlife exhibits this behavior it often escalates to more aggressive behavior, creating a dangerous situation for visitors.”

The park defended its decision to euthanize the elk, saying the choice was not “made lightly.” This is the first time the park has euthanized an elk.

"This was not a one-time incident," Dana Soehn, spokeswoman for the park, told the Asheville (N.C.) Citizen-Times of the elk’s bold behavior. "[The video] was a trigger; the physical contact escalated our decision."

The park said it had had trouble with the young bull approaching park visitors in the past. “The elk had likely been fed by visitors and had lost his instinctive fear of humans,” the statement reads. “It associated humans with food and had been approaching visitors seeking handouts.”

According to NBC News, park officials said they had attempted to “haze” the elk 28 times. Hazing means that rangers shot the animal with bean bags and paint balls, chased it, and even lit firecrackers in an effort to scare the animal away from people.

"This fall, there have been several elk that have become food-conditioned," Soehn said, according to USA Today. "We have reports of visitors who have been feeding them and the elk have been getting closer and closer. ... that one potato chip does make a big difference."

In the viral video, dated Oct. 20 and uploaded to YouTube last week by Vince Camiolo, the elk is seen playfully interacting with photographer James York, including gently head-butting him. York can be seen sitting on the side of the road along the Cataloochee Trail snapping photographs. York told reporters that he wished he had never been there to photograph the elk in the first place, knowing that the encounter partly led to the elk being euthanized.

"All the joy is gone,” York told WBIR. “No one got hurt, so it was a fun ride. I know the attention contributed to the animal being put down and I wish it had never happened.”

“I am deeply saddened by the fate of the elk,” Camiolo said in a statement on his YouTube page. “It has certainly pulled a black cloud over this whirlwind ‘viral video’ experience.”

Camiolo told NBC News he felt partly responsible for the elk’s fate. He said he was “really shaken” by the news that park officials had euthanized the animal.

Elk are relatives of deer but are much larger. According to National Geographic, adult elk can reach 4 to 5 feet in height at the shoulder and weigh between 325 and 1,100 pounds. A bull elk’s antlers can reach nearly 4 feet long.

Elk were once common across North America hundreds of years ago, but have since disappeared after many of them were killed off or driven to more remote locations. Today, elk are concentrated mainly in western North America, especially in the mountainous regions. Some eastern U.S. states, like those around the Appalachian Mountains, have begun to reintroduce elk herds to wooded areas.