President Joe Biden made a surprise virtual appearance at the Marjory Stoneman Douglas High School graduation ceremony on Tuesday, telling survivors of a 2018 mass shooting that “there’s no question you’re already changing the world.” (Watch above)

The 2021 graduates were freshman in February 2018 when one of their classmates shot and killed fourteen students and three staff members at the Parkland, Florida school. Nine of the victims would have graduated this week. Instead, their parents were given their diplomas.

“Three years ago, your lives and the lives of this community changed in an instant. This class lost a piece of its soul,” Biden said via taped remarks from the East Room of the White House. “You’ve been tested in ways no young person should ever have to face.”

Many survivors of the attack became gun control activists.

“No graduation class gets to choose the world in which they graduate,” Biden continued. “But every once in a while, every few generations, young people come along at a point in history with a chance to make real change. The world has already seen just how capable you are, how strong you are, how resilient you are.”

Biden added that graduating class embodies a story of  “turning pain to purpose, darkness to light. This is the legacy you’re building, the legacy you’ll continue to build.”