David is a student at Marjory Stoneman Douglas High School in Parkland, Florida where the third worst school shooting in U.S. history occurred on Valentine’s Day. The 17-year-old, who was hiding in a classroom with other students when Nikolas Cruz allegedly opened fire with an AR-15 assault rifle, says once he realized it wasn’t a drill, he began to record the events on his cell phone.

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“What I decided to start doing is asking questions to these people so that if our souls were left behind, our voices would echo on,” David tells Dr. Phil on Thursday’s episode.

Hear more of David’s story in the video above, and see what he captured on his phone.

WATCH: Teens Describe What It Was Like During The Mass Shooting At Their Florida High School

And on Thursday, hear from other Parkland students. Plus, hear what two survivors of the Columbine High School shooting 19 years ago have to say to these students. Check here to see where you can watch.

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Father Of Florida High School Student Caught In Mass Shooting: ‘It Was The Worst Nightmare Ever’