While driving down a deserted highway in Yellowstone National Park, a man gets a surprise of his life.
Alex Wypyzinski told CNN he heard a loud noise that sounded to him like "a horse and carriage."
He looked in his rear-view mirror and spotted two brown blurs darting down the highway. His initial thought: it was moose.
But as they animals thundered towards him, he noticed a much more rare sight: a grizzly bear hunting an injured bison. So he grabbed his camera and then snapped away before telling CNN his story.
Watch what it was like from his perspective above.