0542 GMT March 17, 2018
"To every politician taking donations from the NRA, shame on you!" said Emma Gonzalez, assailing Trump over the multimillion-dollar support his campaign received from the gun lobby - and prompting the crowd to chant in turn: "Shame on you!"
Wednesday's massacre, which claimed 17 lives at Marjory Stoneman Douglas High School, has fueled urgent calls for an end to the national deadlock over gun control – with a string of shooting survivors rallying behind the cause, AFP wrote.
The gunman, 19-year-old Nikolas Cruz, was able to legally buy an assault rifle despite a history of troubling and violent behavior.
In Washington, however, the political response has made clear that the powerful NRA pro-gun lobby remains formidable, while Trump himself suggested the root cause of mass shootings was a crisis of mental health – making no mention of gun control.
"If the president wants to come up to me and tell me to my face that it was a terrible tragedy and... how nothing is going to be done about it, I'm going to happily ask him how much money he received from the National Rifle Association," said Gonzalez.
"It doesn't matter because I already know. Thirty million," she told the rally attended by fellow students, parents and local officials, citing the sum spent by the NRA to support Trump's election bid and defeat Hillary Clinton.
Dividing that sum by the number of shooting victims in the United States so far this year, Gonzalez asked: "Is that how much these people are worth to you, Trump?"
The young woman's powerful address immediately went viral, with her name a top trending topic on Twitter.
The US leader also tweeted a day after the massacre that that neighbors and fellow students had failed to flag Cruz to the authorities.
"We did," Gonzalez said, her shaking with emotion. "Time and time again. Since he was in middle school. It was no surprise to anyone who knew him to hear that he was the shooter."
US authorities have come under mounting scrutiny for failing to act on a series of warning signs.
The FBI admitted on Friday it received a chilling warning in January from a tipster who said Cruz could be planning a mass shooting, but that agents failed to follow up.
Trump said Saturday the FBI was so caught up in the Russia probe that it failed to heed signs which could have prevented the Parkland school shooting.
His comments came as he faces criticism from survivors of the attack over his ties to the powerful National Rifle Association, and after several thousand rallied in Florida to demand urgent action on gun control.
"Very sad that the FBI missed all of the many signals sent out by the Florida school shooter. This is not acceptable," he wrote on Twitter.
"They are spending too much time trying to prove Russian collusion with the Trump campaign - there is no collusion. Get back to the basics and make us all proud!"