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.

Documents found in a search of the home where Patrick Joseph White lived with his parents “expressed the shooter’s discontent with the COVID-19 vaccinations,” authorities said.

Speaking to reporters on Tuesday, Georgia Bureau of Investigations Director Chris Hosey said 500 shell casings were recovered from the scene, while its believed 200 rounds hit six buildings in the CDC complex. Five firearms were also recovered, he said.