Students at the STEM School Highlands Ranch in Colorado stormed out of a vigil honoring their slain classmate on Wednesday evening in anger over what they saw as a “political stunt” using their tragedy to push for gun control.

“We are people, not a statement,” the students shouted as they marched out of the gymnasium at the nearby Highlands Ranch High School. Hundreds of students, teachers, and activists had attended the vigil, which was billed as honoring Kendrick Castillo, a teenager fatally shot when he tried to tackle one of the shooters in a spree on Tuesday that left eight others injured at a charter school in a Denver suburb. Two students, 18 and 16, have been arrested.

The event was organized by a gun control group called the Brady Campaign to Prevent Gun Violence. According to USA Today, many students appeared to have been unaware that the event was organized by an advocacy group. A half-hour in, after Sen. Michael F. Bennett and Rep. Jason Crow of Colorado spoke about gun regulations, the students became furious at what they saw as the politicization of their trauma.

“I thought this was about us, not about politics,” one student said, according to the Washington Post. Another student argued that they were “not a statistic” and shouldn’t be cited to justify gun control: “We are people, not a statement.”

The students held their phones’ flashlights into the air and chanted, “mental health, mental health.” They also confronted journalists, whom the Brady Center had invited to cover the event, calling them derogatory names, according to the Denver Post, and asking to see what photos they had taken.

The Brady Center apologized for the vigil later on Wednesday. “We are here to lift up the voices of victims and survivors,” the statement said. “We are deeply sorry any part of this vigil did not provide the support, caring and sense of community we sought to foster and facilitate.”

According to the Washington Post, some students returned to the gymnasium later to finish the event. “We wanted Kendrick to be mourned,” one student who addressed the crowd said. “We wanted all of you to join us in that mourning. But that was not allowed here.”