(CNN) The discussion over what happened between competing groups of people on the steps of the Lincoln Memorial on Friday doesn't appear to be going away anytime soon.

It all started that evening when someone posted an Instagram video of a tense encounter between a Native American elder and a group of Catholic high school students from Kentucky.

Twenty-four hours later, the video was everywhere: trending on social networks, splashed across news sites and airing on TV.

How did it spread so fast? Here's a closer look.

What happened that day at the Lincoln Memorial

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