Delaney Tarr’s first brush with television cameras came during her freshman year, when she took a production class as an elective. She has taken the class every year since, and as a junior last year, she anchored the school’s news broadcast.

Calm and self-assured — even in moments of chaos — she was a good fit for the role.

Now a 17-year-old senior at Marjory Stoneman Douglas High School in Parkland, Fla., Delaney aspires to be a journalist, said her mother, Jennifer, and she spends part of each school day wandering the halls doing interviews. In the weeks before the shooting massacre on Valentine’s Day, Delaney and her mother discussed what to do if there were an attack there while she was in the halls — teachers had warned her that they would lock classroom doors and she would be unable to get inside. At the time, it felt like a far-fetched scenario, and they tossed around some unusual solutions: Could she hide in a garbage can? Or in the bathroom?

“There’s no lock on the door. You’ll be a sitting duck,” Jennifer recalled telling her. Speaking from a hotel lobby in Tallahassee, where Delaney had gone with other students to rally and meet with state legislators about gun control on Wednesday, Jennifer paused for a moment, catching a glimpse of a CNN broadcast on a nearby television. “Oh, she’s on TV.”

They ultimately decided that Delaney should carry her car keys everywhere, and if shots were fired while she was in a hallway, she would go to her car and crouch down in the hatchback. When the shooting began on Feb. 14, Delaney was in her journalism class — a room outfitted with a large closet to store equipment — and she and her classmates piled inside. She texted her mother that she was keeping other students calm. Her mother tried to keep things light.

“What happens if somebody farts in the closet?” Jennifer said she texted her daughter.

Delaney came home “a wreck,” slept little the night after the shooting and then attended vigils the following day. She then banded with students from the school’s politics club, birthing a campaign for stronger gun restrictions, creating the hashtag #NeverAgain and spawning walkouts in high schools across the country.

As the requests for interviews rolled in, her mother pressed her to make sure she was okay. Did she need grief counseling or a break?

She told her mother: “I’m at anger mode. I’m past the sadness.”

“I don’t know how she does it,” Jennifer said. She said Delaney views herself as a spokeswoman of sorts for students who are too traumatized to speak.

Before Wednesday, Delaney said she was stressed about all the things that would normally preoccupy a high-octane student: putting together restaurant reviews for the school newspaper, assembling a portfolio for the school literary magazine, trying to choose the perfect prom dress. Now she’s written an editorial for Teen Vogue, and appeared on CNN, ABC and the Opposition with Jordan Klepper. This week, she flew from New York City, where she sat for interviews with national media, to Tallahassee — for a rally at the state capitol — and back to Broward County to participate in a town hall hosted by CNN.

Tuesday, she will return to school, but she said she will continue her advocacy for “common sense gun reform,” including raising the minimum age to purchase a firearm and implementing more robust background checks.

“This is not a sprint. This is a marathon,” Delaney said. “This is something we have to keep working on for months, for years even.”