He also criticized politicians and the school system for having the students return to school less than a month after the shooting and failing to provide adequate resources to manage their mental health.
The student's death occurred on Saturday evening and is under investigation, said Coral Springs Police spokesman Tyler Reik.
News of the death comes a week after Sydney Aiello, who recently graduated from the high school, took her own life.
The announcement of the student's death comes on the anniversary of March for Our Lives, the student-led demonstration against gun violence that was held in Washington and several other US cities a year ago, and on the final day before Marjory Stoneman Douglas students return to school from spring break. "Now is beyond the time to invest in the well being of our students and our future", according to Local10.
Sydney was a close friend of Meadow Pollack, who was killed in the shooting.
Meadow's father, Andrew Pollack, told the Miami Herald that his "heart goes out to those poor, poor parents", referring to Sydney's parents.
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Brenton Tarrant , a 28 year-old Australian man, was arrested within minutes of the attack and has been charged with murder. New Zealand police said on their website a "transitional period" would allow people to turn in their guns without penalty.
"It's awful what happened".
Fundraising organisers Brett and Blair Israel are family friends of the Aiellos and wrote on the page that it was a "privilege" to have had Sydney in their lives.
People still affected by the shooting can seek counseling through the Broward County Resiliency Center at Pine Trails Park in Parkland, not far from the Stoneman Douglas campus.
Her mother, Cara Aiello, said that her daughter hesitated to ask for help, and she hopes that her story can help others get the support that they need.
After his daughter's death, Petty launched the Walk Up Foundation to help prevent suicide.
Reik reportedly added: "I know he attended Stoneman Douglas".