PARKLAND, Fla. -- Students who survived the Florida school shooting began a journey Tuesday to the state capitol to urge lawmakers to prevent another massacre, but within hours the gun-friendly Legislature had effectively halted any possibility of banning assault-style rifles like the one used in the attack.

The legislative action further energized the teens as they prepared to confront legislators who have quashed gun-control efforts for decades in a state where 1.3 million people have concealed carry permits.

"They're voting to have shootings continually happen. These people who voted down the bill haven't experienced what we did. I want to say to them, 'It could be you,"' 16-year-old Noah Kaufman said as he made the 400-mile (640-kilometre) trip to Tallahassee.

Three buses carried 100 students who, in the aftermath of the attack that killed 17 people, want to revive the gun-control movement. The teens carried sleeping bags and pillows and hugged their parents as they departed, many wearing burgundy T-shirts in their school colours.

They spent the seven-hour ride checking their phones, watching videos and reading comments on social media about the shooting, some of which accused them of being liberal pawns.

As the grieving Florida students demanded action on guns, President Donald Trump on Tuesday directed the Justice Department to move to ban devices like the rapid-fire bump stocks used in last year's Las Vegas massacre. It was a small sign of movement on the gun violence issue that has long tied Washington in knots.

"We must do more to protect our children," said Trump, a strong and vocal supporter of gun rights. He added that his administration was working hard to respond to the Florida rampage.

Meanwhile at the Florida Statehouse, a Democratic representative asked for a procedural move that would have allowed the Republican-controlled House to consider a ban on large-capacity magazines and assault-style rifles such as the AR-15 that was wielded by the suspect, Nikolas Cruz.

The bill had been assigned to three committees but was not scheduled for a hearing. The House quickly nixed the Democratic motion. The vote broke down along party lines, and Republicans criticized Democrats for forcing the vote.

Because the committees will not meet again before the legislative session ends March 9, the move essentially extinguishes hope that lawmakers would vote on any sweeping measures to restrict assault rifles, although other proposals could still be considered.

"No one in the world with the slightest little hint of a soul isn't moved by this tragedy," Republican strategist Rick Wilson said. "The discussion has to be a longer, bigger and broader discussion."

Lizzie Eaton, a junior at Marjory Stoneman Douglas High School, spent the day lobbying senators of both parties and concluded that lawmakers were "just not listening to us."

The vote was "heartbreaking," she said. "But we're not going to stop."

The students planned to hold a rally Wednesday to put more pressure on the Legislature.

"I really think they are going to hear us out," said Chris Grady, a high school senior aboard the bus.

The Feb. 14 attack initially appeared to overcome the resistance of some in the state's political leadership, which has rebuffed gun restrictions since Republicans took control of both the governor's office and the Legislature in 1999. However, many members of the party still have strong resistance to any gun-control measures.

Republican leaders in the House and Senate say they will consider raising age restrictions for gun purchases and temporarily revoking someone's guns if that person is deemed a threat to others. Gov. Rick Scott, also a Republican, convened groups assigned to propose measures for protecting schools from gun violence.

Lawmakers will probably say that getting a new bill passed is nearly impossible with only two and a half weeks left in the legislative session. Some lawmakers who are thinking of running on a statewide ticket are mindful of their sensitive positions, since gun owners make up huge voting blocs in some parts of the state, especially the Panhandle.

Wilson said he knows the students "want something to happen," and they need "a moment to come and make their case."

But, he said, "the thought that you get to wave a wand and change the law is something that is probably going to collide with reality."

The Parkland students also plan to meet Wednesday with top legislative leaders, including House Speaker Richard Corcoran and Senate President Joe Negron.

Florida has a reputation for expanding gun rights. Negron sponsored a 2011 bill that Scott signed into law that banned cities and counties from regulating gun and ammunition sales.

Authorities said Cruz, 19, had a string of run-ins with school authorities that ended with his expulsion. Police were repeatedly called to his house throughout his childhood. His lawyers said there were many warning signs that he was mentally unstable and potentially violent. Yet he legally purchased a semi-automatic rifle.

The Senate is also considering boosting spending on mental health programs for schools and giving law-enforcement greater power to involuntarily hold someone considered a danger to themselves. The chamber will also look at a proposal to deputize a teacher or someone else at school so they are authorized to have a gun.

Kyle Kashuv, a 16-year-old student at the high school, said he was pro-gun prior to the shooting.

"I had no issue with anyone having a gun of any calibre," said Kashuv, as he rode in the bus to Tallahassee. "I was all for it. But after the situation, I realized we have some issues in our society and it has to be addressed.

The fact that someone who was so steadfast in support of gun rights now acknowledges the need for changes "really shows how important what we're doing is," he said.

Farrington reported from Tallahassee, Florida. Associated Press writers Gary Fineout in Tallahassee and Sadie Gurman in Washington contributed to this report.