HIGHLANDS RANCH, Colorado—A day after two students shot up a school, survivors walked out of a vigil organized by gun control advocates, saying they felt excluded from what should have been an opportunity to grieve.

Team Enough and Moms Demand Action helped promote the Wednesday evening gathering, and more than 100 students and several hundred parents from the STEM School packed into the gymnasium bleachers, hoping to find community and catharsis.

But after sitting through remarks by Rep. Jason Crow (D-CO) and Sen. Michael Bennet (D-CO), and realizing the program was centered around changing gun laws, students who had hoped to speak lost patience and walked out en masse.

“This was not about us. We can do our own vigil,” one STEM student remarked.

“ I feel terrible. They did not feel represented. I get it. ” — Laura Reeves, Moms Demand Action volunteer

Students from Team Enough said the event was organized on such short notice they were unable to find a way to include STEM students in the program.

“I feel terrible. They did not feel represented. I get it,” said Laura Reeves, a volunteer with Moms Demand Action who spoke at the vigil.

“This was put together in such a short time. I know they did their best. Emotions are raw and sad. They are grieving. They need to express their feelings. They need to be together. I am hoping their school can help facilitate that conversation beyond this week.”

Police have said two STEM students opened fire at the school on Tuesday, killing one and wounding eight before they were arrested. Any motive for the attack—20 years after the Columbine High School massacre just seven miles away—has not been disclosed.

Heavy rain had kept surviving students cooped up at home, and many of them were looking forward to the vigil at a neighboring school. Things began to fall apart an hour in when organizers suggested any STEM students who wanted to speak gather in the hall outside the gym.

A few rose to speak, but soon the crowd filed out and left. Standing outside the building in the freezing rain, some began chanting. But they quickly dispersed as Douglas County Sheriff's vehicles began arriving at the school.

One mom of a STEM student said it was a case of good intentions gone wrong.

“I really appreciate what they tried to do here tonight, but our kids didn’t want to be talked at,” she said.