The U.S. CDC has tightened security following an attack Friday on its Atlanta headquarters that left a police officer and the gunman dead, including having most employees work from home this week and removing vehicle decals showing where they work.

Officials are still investigating a shooting at the Centers for Disease Control and Prevention headquarters in Atlanta, Georgia, that killed a police officer on Aug. 8. The suspect, Patrick Joseph White, 30, may have been disgruntled over vaccine side effects before perpetrating the shooting, according to multiple reports.

The CDC issued a nationwide notice for all staff and employees following Friday’s deadly shooting outside the Atlanta headquarters.