CNN —  

Not even a month ago, students at Santa Fe High School took a stand against gun violence by walking out of their classrooms in solidarity with their peers across the nation.

From @mukethemusical/Twitter

With signs that read “Santa Fe High School SAYS #NeverAgain,” they sat outside for 17 minutes of silence.

From @mukethemusical/Twitter

Today, the same students were left reeling from a shooting at their own school.

Nine students and one teacher were killed, 10 others were wounded, a law enforcement official told CNN.