A student had a message for politicians Thursday, the day after he survived a mass shooting that killed 17 people and injured 15 others at his high school in a South Florida suburb.

“Please, take action. Ideas are great. Ideas are wonderful and they help you get reelected and everything,” David Hogg said on CNN as he looked straight at the camera. “But what's more important is actual action ... that results in saving thousands of children's lives. Please, take action.”

Hogg, a senior, said he was in an AP environmental science class Wednesday afternoon when he heard a gunshot. Then the fire alarm went off. Hogg said he and his classmates went out to the hallway, thinking the school was doing a fire drill. As they were walking, “a flood of people came along,” he said.

“They said, 'Don't come this way, don't come this way. He's coming this way,'" Hogg told The Washington Post's Whitney Shefte.

The Valentine's Day massacre at Marjory Stoneman Douglas High School in Parkland, Fla., northwest of Fort Lauderdale, is the deadliest public school shooting since 20 first-graders and six staff members were killed at Sandy Hook Elementary in Newtown, Conn., in 2012. It's also one of the deadliest mass shootings on record.

Authorities say the gunman, armed with an AR-15 rifle, planned the mass murder. He pulled a fire alarm and waited for students and staffers to crowd the halls. Police say Nikolas Cruz, a former student who had been expelled for disciplinary problems, had several magazines of ammunition.

Hogg said a culinary teacher kept him and several other students safe inside a classroom. The student journalist then pulled out his camera and interviewed classmates while they were in hiding. A video posted on YouTube by Storyful, which vets user-generated videos and photos, shows students being interviewed inside a dimly lit room.

“This shouldn't be happening anymore and ... it doesn't deserve to happen to anyone,” a female student said nervously. “No amount of money should make it more easily accessible to get guns.”

As the camera went out of focus, another female student began talking. She rallied for gun rights and wanted to be a junior member of the National Rifle Association, she can be heard saying. She said she was planning to go to a gun range for her 18th birthday to learn how to shoot. All of that has changed.

“I don't even want to be behind a gun,” she said. “I don't want to be the person behind a bullet. I don't want to be the person to point a bullet at someone. And to have the bullet pointed at me, my school, my classmates, my teachers, my mentors. It's definitely eye-opening to the fact that we need more gun control in our country.”

School shootings have happened so often in the United States that she said people have become inured to the threat, she said.

“I even texted my sisters, 'Shooting at my school. I am safe,'" the girl said. “They responded, 'OMG, LOL, you're funny.' Now that's a problem in society, and it's a bigger problem in America.”

Hogg said he decided to start recording to make sure he would have a story to tell, in case he died.

“A story that would echo on and show people that there's a serious issue in this country that people need to face, take a long, hard long at, and realize [that] blood is being spilled on the floors of American classrooms,” he said.

Cruz has been charged with 17 counts of premeditated murder, and investigators are still piecing together what allegedly drove the 19-year-old to commit the rampage. A partial portrait, though, has emerged. Cruz had been showing signs of depression and had stopped going to a mental health clinic for treatment, The Washington Post reported. His mother died around Thanksgiving, and his father, a few years ago. Social media posts show a fascination with guns and shooting animals.

In a tweet Thursday morning, President Trump pointed to signs that Cruz was “mentally disturbed.”

“Neighbors and classmates knew he was a big problem,” Trump said. “Must always report such instances to authorities, again and again!”

Asked by CNN on Thursday about what kind of action Trump and lawmakers need to take, Hogg said that “any action” is better than “complete stagnancy” and political finger-pointing.

“We can say, 'Yes, we're going to do all these things. Thoughts and prayers,'” Hogg said. “What we need more than that is action. Please, this is the 18th one this year. That's unacceptable. We're children. You guys are the adults. You need to take some action and play a role.”

Hogg may have been referring to statistics from Everytown, a gun-control advocacy group that has tallied 18 school shootings since January. The tally includes accidental shootings, suicides and incidents in which no one was injured. As The Post's John Woodrow Cox and Steven Rich reported, that number is inflated and included incidents that are not really school shootings.

Jim Lewis, the attorney representing the family who took in the Fla. shooting suspect, said that the family noticed noticed nothing out of the ordinary. (Alice Li/The Washington Post)

Correction: This post originally said Nikolas Cruz used a gas mask and smoke grenades during the shooting. On Friday, Broward County Sheriff Scott Israel said neither were used.

Read more: