Trump made the comments Wednesday during a listening session at the White House with survivors of the mass shooting at Marjory Stoneman Douglas High School in Parkland, Fla. Nikolas Cruz, a former student at the school, allegedly used an AR-15 semi-automatic assault rifle to kill 17 students and educators.

“This would obviously only be for people very adept at handling a gun,” Trump said. “It’s called concealed carry, where a teacher would have a concealed gun on them, they’d go for special training, and they would be there and you would no longer have a gun-free zone.”

“A gun-free zone to a maniac—because they’re all cowards—a gun-free zone is ‘Let’s go in and let’s attack because bullets aren’t coming back at us,'” Trump continued.

Trump’s comments came after he asked those attending the event for ideas about how to stop school shootings. One parent suggested teachers could volunteer and receive training to carry guns in schools to fight back against would-be mass shooters before first responses arrive.

Trump also mentioned that professional armed guards such as retired Marines could prevent attacks at schools. He linked some airline pilots carrying guns to a decline in airplane hijackings as well. He didn’t mention other additional security measures like tougher airport screenings and reinforced and locked cockpit doors.

The president asked the parents and students who were at the White House if they were strongly opposed or liked the idea. There appeared to be a mixed reaction, based on video of the session.

“We can understand both sides, certainly it’s controversial,” Trump said in response. “But we’ll study that along with many other ideas.”

There was an armed security guard on duty at Marjory Stoneman Douglas High School on the day of the shooting, according to the Broward County Sheriff. The armed guard never encountered Cruz, who allegedly pulled a fire alarm and opened fire on students as they filed out of their classrooms.

Trump isn’t the first person to suggest teachers carry concealed weapons. Nor is this the first time Trump has proposed the idea. In 2016, presidential candidate Hillary Clinton accused Trump of wanting to “mandate that every school in America allow guns in classrooms” after Trump said he would eliminate gun-free zones in schools. Trump initially disputed Clinton’s accusations. He later clarified that only “school resource officers” or trained teachers should be the ones carrying guns.

Crooked Hillary said that I want guns brought into the school classroom. Wrong!

— Donald J. Trump (@realDonaldTrump) May 22, 2016

In Ohio’s Butler County, hundreds of teachers and school employees signed up for a concealed weapons class offered by their sheriff following the Florida school shooting. However, it’s not clear that teachers would be able to bring them into the schools. Ohio’s concealed carry law requires school employees leave their guns in their locked car when they’re in a school safety zone, unless they have written permission from the school district to do otherwise, reported CNN.