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.

The suspected gunman in the shooting of a police officer at the headquarters of the Centers for Disease Control and Prevention (CDC) in Atlanta on Friday has been identified as Patrick Joseph White of Kennesaw,

Authorities said Tuesday that investigators recovered at least 500 shell casings at the scene, estimating that White fired more than 180 shots at the CDC headquarters using his father’s long gun. White shot and killed himself at the scene before responding officers could reach him.