While visiting Yellowstone National Park a tourist decides to pet a bison.  The animal is caught on video near the boardwalk with numerous other tourists and children nearby.  In the video below you can watch the man approach the bison and pet the bison's forehead area.  When the man reaches back towards the bison for another touch the agitated bison darts away.

In the video you can hear the person recording whisper "no" numerous times and even states "don't do it."  Perhaps the tourist should have aided the camera man's advice, though he did walk away unscathed.

Yellowstone National Park officials do advise people to give animals their space and when they are near a trail, boardwalk, parking lot, or in a developed area. Be sure to stay 25 yards away from all large animals such as bison, elk, bighorn sheep, deer, moose and coyotes.