Justin Blackman walked out of class at Wilson Preparatory Academy on Wednesday, as did students all over the country, to protest gun violence after last month's mass shooting at a Florida high school that killed 17 people.
But when Blackman got outside of his school, he realized he was the only one participating.
He posted a video on Twitter, saying: "It's National Walk Out Day and I'm the only one at my school out here."
Since then, the tweet has gone viral.
As of 5:45 p.m., the video had two million views, more than 22,000 retweets and 100,000 likes.
In the video, Blackman said his teacher let him leave class.
Janet Conner-Knox, who handles public relations for Wilson Preparatory Academy, told CNN: "We teach our students to be independent thinkers. (Blackman) is an independent thinker."