Wenk said Yellowstone bison should be managed like wildlife rather than livestock and the herd's size should not be exclusively determined by ranchers who live outside the park in Montana. Some of the visitors got even closer, agitating the bison and provoking it to cross the boardwalk and charge into Hancock. The animal left the area after goring Hancock.
Hancock sustained a hip injury, but was in good condition after being transported to a nearby hospital, the park service said.
Conflicts have raged for years over how many bison the park can sustain and methods used to keep the population contained.
There have been two bison attacks so far in 2018.
Environmentalists on Friday accused the Trump administration of political interference and retaliation in the ouster of Yellowstone National Park's chief after his disputes with U.S. Interior Secretary Ryan Zinke over the park's celebrated bison.
Four people have been injured by wildlife at Yellowstone in the past month. Because of the severity of her injuries she was flown to an Idaho trauma center.
Kim Hancock, 59, was gored by the animal and taken to a medical facility, where she is recuperating.
Park officials not that it's very common for cow elk to aggressively defend newborn calves and hide them near buildings and cars. In 2017, there was only one incident at Yellowstone of a visitor being injured by a bison while 2015 saw five such incidents.
"I'm feeling like I devoted 43 years of my life, I think I have a record of achievement with the National Park Service that at the end of the day doesn't matter and that I'm no longer wanted at Yellowstone National Park", he said.
A crowded boardwalk in the Lower Geyser Basin in Yellowstone National Park on August 18, 2015.