Bear vs. bison at Yellowstone National Park

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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.