Thousands of angry American students, parents and residents have demanded stricter gun control laws, as new details were revealed about the suspect accused of killing 17 people in a Florida high school.
The rally, held in central Fort Lauderdale, was attended by scores of students from Marjory Stoneman Douglas High School, where the shooting happened.
Teenagers spoke passionately during Saturday's rally in front of the federal courthouse, pleading with legislators to change the nation's gun laws.
One student, Emma Gonzalez, angrily criticised politicians who take campaign contributions from the National Rifle Association. She challenged them to stop taking money, leading the crowd in a call-and-response chant.
"They say a good guy with a gun stops a bad guy with a gun," she said, and the crowd chanted, "We call BS."
She also said adults who knew that the shooter was mentally ill should have done more to prevent him from having a weapon.
New evidence suggests Nikolas Cruz was unstable and violent to himself and those around him - and that when notified about his threatening behaviour, law enforcement did little to stop it.
He reportedly left a suburban Palm Beach County mobile home in November because his benefactor threatened to remove him if he kept a gun.
The Palm Beach Post reported Rocxanne Deschamps said: "He bought a gun and wanted to bring it into my house" in public comments that have since been removed from her Facebook page.
Chad Bennett, a friend of Ms Deschamps, said Cruz "chose the gun and he left".
He then went to live with another family; his mother died in November and his father died years ago.
Florida's child welfare agency investigated after he cut himself in an online video but found him stable, according to state records.
The Sun-Sentinel reported that Florida's Department of Children and Families (DCF) investigated when Cruz posted a video on the social media network Snapchat showing him cutting his arms in 2016.
The agency was called to investigate. Cruz, then 18, was listed as an "alleged victim" of medical neglect and inadequate supervision.
His adoptive mother, then-68-year-old Lynda Cruz, was named as the "alleged perpetrator".
"Mr Cruz was on Snapchat cutting both of his arms," the Florida DCF abuse hotline was told in August 2016, the paper reported.
"Mr Cruz has fresh cuts on both his arms. Mr Cruz stated he plans to go out and buy a gun. It is unknown what he is buying the gun for."
According to the paper, the DCF's investigation was completed that November. The agency concluded that Cruz had not been mistreated by his mother, was receiving adequate care from a mental health counsellor and was attending school.
Mental health centre staff "came out and assessed the (victim and) found him to be stable enough not to be hospitalised," the DCF report said.
Cruz had been diagnosed with autism, a neurological disorder that often leads to social awkwardness and isolation, and attention deficit-hyperactivity disorder, or ADHD.
The FBI said it received a tip-off last month that Cruz had a "desire to kill" and access to guns and could be plotting an attack, but agents failed to investigate. The governor called for the FBI director to resign.
In a statement, the agency acknowledged that the tip should have been shared with the FBI's Miami office and investigated, but it was not.
The admission came as the agency was already facing criticism for its treatment of a tip about a YouTube comment posted last year.
The comment posted by a "Nikolas Cruz" said: "I'm going to be a professional school shooter."
The FBI investigated the remark but did not determine who made it.
Attorney General Jeff Sessions said the shooting that killed 17 people on Wednesday was a "tragic consequence" of the FBI's missteps and ordered a review of the Justice Department's processes. He said it is now clear that the nation's premier law enforcement agency had missed warning signs.
Broward County Sheriff Scott Israel said his office had received more than 20 calls about Cruz in the past few years.
Cruz faces 17 counts of first-degree murder in the shooting at Marjory Stoneman Douglas High School, and is being held at the Broward County Jail without bond.
Additional reporting by the Press Association