David Hogg on the movement against gun violence, five years after Parkland

"It feels like a lifetime has gone by," said David Hogg. It was February 14, 2018, when Hogg, then 17, and other terrified students at Marjory Stoneman Douglas High School in Parkland, Florida, sheltered in classrooms and closets as a 19-year-old gunman rampaged through their school.

"I was really, really scared, and I kind of felt like the adrenaline had rushed down my spine. But I immediately heard in the back of my head my dad's voice: 'If anything ever happens, you have to stay calm.'"

So, locked down with other students, Hogg started recording videos, in case they didn't survive.