Saturday will mark 20 years since the shooting at Columbine High School, when two teen gunmen claimed the lives of 13 people.
Journalist and author Dave Cullen said the attack wasn't America's first school shooting, "but it was the first horrific one." After the shock of Columbine, American parents for the first time became afraid to send their kids to school. "And that changed everything," he said.
Since the April 20, 1999, Columbine shooting, massacres have unfolded at other schools across the United States, including one last year at a high school in Parkland, Florida, that killed 17. Cullen, who has written books about both the Columbine and Parkland shootings, said student reactions to those attacks were "night and day."
"For Columbine, what's really seared into my memory is Day 2," he said. After the horror and "pandemonium" of the attack — the following day was "completely different."
"I got there at 10 in the morning and there were no tears," he said. "And the boys, especially, there was like no emotions." He said they were "really scared to death."
In Parkland, however, kids did show emotion. Cullen said so many of those kids said, "'I was kind of expecting it. … Our school or somebody else's school.'" The students in Parkland — born after the Columbine shooting — went to kindergarten or preschool doing lockdown drills, Cullen said.
"That's just their life," he said. "Sometimes, you get murdered at school. ... I think adults lose sight of that. And that's why those kids are so angry ... because they know that it is wrong."
Within days of the shooting at their school on Valentine's Day last year, students in Parkland mobilized,that has demanded a change in gun laws and sparked a national conversation.
Cullen said that during the first 19 years after Columbine, America "did nothing" — until the Parkland shooting.
"Columbine really started the mass shooting era and Parkland is hopefully the beginning of the end, or the way out," he added.