The 16-year-old suspect in the Evergreen High School shooting was radicalized by online posts about white supremacy and mass shootings, according to a report from the Anti-Defamation League.

The suspected shooter, Desmond Holly, opened fire at the Denver-area high school on Wednesday, critically injuring two other students before dying from a self-inflicted gunshot wound. Before the shooting, Holly posted neo-Nazi views on his social media accounts and was active on online threads that depicted extremely graphic violence, the ADL’s Center on Extremism said in a published analysis.