Donald Trump hosted a group of students, parents, and teachers at the White House today to talk about how the US can prevent school shootings, in the wake of last week’s lethal school shooting in Parkland, Florida.

Several student survivors from Parkland’s Marjory Stoneman Douglas High School spoke, as well as parents who had lost children there. Also present were the parents of students killed in 1999 at Columbine High School, and in 2012 at Sandy Hook Elementary.

Invited by Trump to propose solutions to school shootings, the visitors’ suggestions ranged from heightened school security to better mental health facilities, with several speakers carefully avoiding the topic of guns. Some dedicated their speaking time to thanking the president for his leadership.

Sam Zeif, a senior at Stoneman Douglas, was the first student to forcefully bring up the topic of guns. He focused particularly on banning assault weapons, like the AR-15 used by Zeif’s former classmate, teenage gunman Nikolas Cruz.

“I lost a best friend, practically a brother and I’m here to use my voice because I know he can’t. And I know he’s with me, cheering me on to be strong, but it’s hard,” Zeif said. He and his friends get spooked when a car drives by, and they’re scared to walk into a public park now, he said.

Then he began into an emotional appeal to regulate the kinds of guns that killed 17 at his high school:

I don’t understand. I turned 18 the day after. Woke up to the news that my best friend was gone. And I don’t understand why I can still go in a store, and buy a weapon of war. An AR. I was reading today that a person, 20 years old, walked into a store and bought an AR-15 in five minutes, with an expired ID. How is it that easy to buy this type of weapon? How did we not stop this after Columbine, after Sandy Hook? I’m sitting with a mother that lost her son.

It’s still happening. In Australia, there was a shooting at a school in 1999 [sic]. And you know, after that, they took a lot of ideas, they put legislation together, and they stopped it. Can anyone here guess how many shootings there have been in the schools since then in Australia? Zero. We need to do something. And that’s why we’re here. So let’s be strong, for the fallen who don’t have a voice to speak anymore, and let’s never let this happen again. Please. Please.

Zeif was apparently referencing a 1996 shooting in Australia, when 35 people were killed with a semi-automatic rifle. After the shooting, the Australian government outlawed the weapons, and over 650,000 guns were turned in to authorities.

There has not been another mass shooting in Australia since then, the 18-year-old noted.

Zeif spoke later about the US constitution’s second amendment, and the state of Maryland’s gun control tactics:

They have proven that the Second Amendment does not protect these types of weapons. They have banned over 45 different kinds of assault weapons, including the AR. Including the AR. They have limited magazines sizes. They have proven that it’s not like we have to lose our Second Amendment. You know, the Second Amendment, I believe, was for defense. And I fully respect that, like I said. But these are not weapons of defense. These are weapons of war. And I just, I still can’t fathom that I, myself, am able to purchase one.

Zeif’s texts with his younger brother Matthew, who was hiding one floor above him during the Parkland shooting, circulated on the internet during the shooting. His brother’s teacher Scott Beigel was killed while ushering students into a classroom for safety; Matthew was one of the last students that he saved.

Calls for gun control rose in the US after Sandy Hook and the Columbine shooting, but were defeated by Congress. While students and parents spoke to the president again today, students from other high schools across the country were organizing and demonstrating in state capitals, including at a gun control rally in Tallahassee, Florida.

“Thank you for pouring out your hearts,” Trump said at the end, “because the world is watching.”