HARTFORD, Conn. (AP) — What started with a Connecticut student's online petition and a meeting at a coffee shop last week has quickly grown into a planned national high school walkout on April 20 to demand action on gun violence following the deadly Florida high school shooting.

More than 150,000 people by Friday had signed the petition, organizers said. It is one of several efforts by young people across the country to stage protest walkouts.

The work of Ridgefield High School sophomore Lane Murdock and two seniors at her school, debate team partners Paul Kim and Max Cumming, has attracted the attention of Connecticut's Democratic congressional delegation.

The lawmakers have pushed unsuccessfully for stronger gun control measures since the 2012 mass shooting at Sandy Hook Elementary School in Newtown. They see action by high school students in Florida, Connecticut and elsewhere since the Feb. 14 Parkland, Florida, shooting, which left 17 dead, as a hopeful change in what's been an intractable debate over tightening federal gun laws.

"We are going to stand on their shoulders and we're going to say, 'enough is enough,' and take action," said U.S. Rep. Rosa DeLauro, who appeared with the teens on Friday at a state Capitol news conference. "That's what this is about now."

Mark Barden, whose 6-year-old son Daniel was killed in the Newtown school shooting, also was at the news conference. He called the young people getting involved since the Florida shooting "a force to be reckoned with."

"They are not going to be intimidated by corporate greed, they're not going to be bullied by money and power. They want to fix this and they're going to do it," he said.

Murdock said she felt sad after first hearing about the shooting at Marjory Stoneman Douglas High School, but she went on with her day as usual. But she said she grew concerned about being unaffected by it initially.

"The fact that I had such a numb reaction to something like this is not OK. This should not be a normalcy. This should not be OK," Murdock said. "So that's why I decided to make my petition."

She then enlisted the help of Kim, who has a reputation for being involved in school activities, via text the day after the shooting, and he got Cumming involved.

"So, when I met at Starbucks and heard Lane talk a little bit — it was the first time we had ever met face-to-face — I just knew that we were onto something incredible," said Kim. The three have been meeting nightly ever since.

There are various efforts underway by students and groups working to stage their own protests and walkouts. The walkout proposed by Murdock falls on the 19th anniversary of the deadly shooting at Columbine High School in Colorado. She said she heard from students across the country and in the United Kingdom, Australia and New Zealand who are interested in participating. At the same time, she is also working to continue the conversation among young people about combatting gun violence after April 20.

"We will not stop working," she said, adding how it's important for students to stay engaged and motivated.

"Adults have been in power for a long time and not a lot has changed," Murdock said. "It's students' time. It's our time."

Cumming said he feels a special obligation to get involved because he lives in Connecticut, where 20 first graders and six educators were gunned down in Newtown, a community a just few towns north of Ridgefield.

"I was in middle school at the time. I remember my school was put on lockdown when Sandy Hook happened because we were so close and didn't know what was going on. So it is a particularly close-to-home issue," he said.

"These people lost little children and there were educators who were killed as well," Cumming said. "And it's been five years. We don't spend every single day thinking and talking about what happened, but they do. And that is the mind-blowing scale of this to me."