(CNN) A student who witnessed Wednesday's massacre at a Florida school made a direct plea to lawmakers on Thursday to take action, warning more children will die otherwise.

"Some of our policymakers and some people need to -- they need to look in the mirror and take some action because ideas are great but without action, ideas stay ideas and children die," Marjory Stoneman Douglas High School senior David Hogg told CNN's "New Day."

At least 17 people were killed Wednesday afternoon when, authorities say, a 19-year-old former student opened fire at the Parkland school near Fort Lauderdale. Nikolas Cruz has been charged with 17 counts of premeditated murder, the Broward County Sheriff's Office said.

Hogg, who is a student journalist, recorded footage of the shooting, but "New Day" anchor Alisyn Camerota explained that it can't be shown on air because of its graphic nature.

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