Public health workers and gun safety advocates gathered at a rally Tuesday night to commemorate last week’s deadly shooting near Emory University and the Centers for Disease Control and Prevention, and demand policy changes to prevent future instances of gun violence.

Documents found in a search of the suspect’s home “expressed the shooter’s discontent with the COVID-19 vaccinations,” Georgia Bureau of Investigation Director Chris Hosey said.

CDC security guards stopped White from driving into the campus on Friday before he parked near a pharmacy across the street and opened fire from a sidewalk. The bullets pierced “blast-resistant” windows across the campus, pinning employees down during the barrage. More than 500 shell casings were recovered, the GBI said.