Officer Mark Morgan of Emory University Police fired at gunman Patrick Joseph White during the shooting at the CDC campus.

All CDC employees nationwide, except for essential on-site personnel, have been instructed to work remotely on Monday as Georgia investigators continue probing Friday's deadly active shooter incident near the agency's Atlanta headquarters, according to a letter obtained by ABC News.

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.