The gunman in the fatal attack on the US Centers for Disease Control and Prevention took his own life after he unsuccessfully attempted to leave the building from where he opened fire, according to a law enforcement source with direct knowledge of the investigation.

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.