"Kennedy is directly responsible for the villainization of CDC's workforce through his continuous lies about science and vaccine safety, which have fueled a climate of hostility and mistrust," one ex-employee wrote, according to the Associated Press news agency.

The 30-year-old shooter also tried to get into the CDC’s headquarters in Atlanta but was stopped by guards before driving to a pharmacy across the street and opening fire late Friday afternoon, the official said.

Patrick Joseph White has been identified as the gunman who killed a policeman before being found dead at the scene.