The teen who marched alone last month, attracting the attention of the country, just got his classmates to join a student walkout in memory of the 15 victims of the 1999 shooting at Columbine High School.

Justin Blackman received massive support on social media last month for being the only student at his high school to participate in the nationwide walkout, part of movement led by Parkland survivors that called for lawmakers to pass stricter gun laws.

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"It's National Walkout Day, I'm the only one from my school out here," the 16-year-old said in a video he tweeted. “I’m just going to be chilling here for the next 15 minutes.”

The video was viewed 6.11 million times.

"Now, I truly know that one person is all it takes," he told CNN, "No matter the age, skin color, gender—it doesn't matter."

When Blackman walked out of class again on Friday, this time, his classmates from Wilson Preparatory Academy joined him.

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He tweeted a photo and video of the walkout showing the groups of people who came out.

Parkland survivor Lexi Tracton responded with encouragement: "Before it was just you walking out, now they follow by your lead and rally with you."

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Matt Deitsch, a March for Our Lives strategist, called Blackman "a modern hero."

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Since tweeting his initial video, Blackman has become a young activist. He met the governor of North Carolina earlier this month and is attending a town hall at University of North Carolina this week.

As he tweeted last month, "I'm young and I HAVE A VOICE!!!!"