Moments before a 17-year-old unleashed gunfire at Iowa’s Perry High School, killing a sixth grader and wounding five other people, the student is believed to have posted a foreboding TikTok video.

On the morning shooter Dylan Butler opened fire, a TikTok post believed to be from the shooter shows him the inside a school bathroom posing with a blue duffel bag, captioned: “Now we wait.”

The song “Stray Bullet,” by the German band KMFDM, accompanies the post, which has been removed from the platform; the student gunmen who carried out the 1999 massacre at Columbine High School in Colorado also had cited the group’s lyrics, CNN has reported.

Butler – who also died amid Thursday’s horror, a law enforcement official told CNN – “made a number of social media posts in and around the time of the shooting,” said Mitch Mortvedt, assistant director of the Iowa Department of Public Safety Division of Criminal Investigation. “Law enforcement are working to secure those pieces of evidence,” he added.