The group's leaders addressed it to candidates seeking the 2020 US presidential nomination, urging them to make gun control a top priority.
Cruz said he had attempted suicide two months before the attack with an overdose of the painkiller Ibuprofen.
Parkland school shooter Nikolas Cruz wants to donate his inheritance -- which could run to hundreds of thousands of dollars or more -- to the bereaved families and survivors of his attack, his lawyers said Wednesday.
At least six companies said on Thursday they were dropping advertisements from Laura Ingraham's Fox News show after the conservative pundit mocked a teenage survivor of the Florida school massacre on Twitter and he responded with a call for a boycott.
Activists and volunteers place 7,000 colorful pairs of donated children's footwear side by side to commemorate those who have died.
Florida school shooter Nikolas Cruz was indicted Wednesday on 17 counts of murder and 17 more of attempted murder, the state attorney's office said.
A dozen protesters gathered outside the event on Wednesday, holding up posters that read "Worship God, Not Guns".
Trump has also called for boosting school security, and controversially, arming some teachers and staff in addition to on-campus guards.
Children, parents and teachers want schools to be safe sanctuaries for teaching and learning, not armed fortresses.
At the forefront were websites known for relaying bogus theories, including the notion that the shooting at Sandy Hook Elementary School was a hoax.
But others disagree, saying that nobody wants to see a shootout in a school.
Gun ownership is protected by the Second Amendment of the US Constitution and remains one of the nation's more divisive issues