Cruz had been expelled from Marjory Stoneman Douglas high school in Parkland, Florida, for disciplinary reasons, according to Broward County sheriff Scott Israel.
The suspect, 19-year-old former student Nikolas Cruz, is in custody.
Nikolas Cruz is detained by police after the deadly shooting.
According to BuzzFeed News, a "former classmate" said that Cruz "complained about bullying". He was armed with a single AR-15 style assault rifle and was carrying "countless magazines, multiple magazines", Israel said.
Jim Gard, a math teacher who says he had Cruz in his class, told the Miami Herald that the young man had attracted the school's notice, as well. We are working closely with law enforcement on the bad Florida school shooting.
Another student said that he knew something was off when the second fire alarm went off.
"We will pay the funeral expenses of these poor victims and do everything we can to help their families", Bondi said.
Law enforcement officials are still investigating the motive of the shooter at this time.
"We routinely run drills or institution to be ready for instances like this so we have a process in place that gets initiated, so there's calm, collected care that our patients receive", Dr. Boyar said.
Police have confirmed that 12 of the victims died inside the school.
Florida Gov. Rick Scott said he had been in contact with local authorities about the episode and would continue to follow the events on the ground.