The gunman who opened fire Friday at the US Centers for Disease Control and Prevention broke into his father’s safe to get the five firearms recovered at the scene, state investigators said Tuesday, as some CDC workers seeking answers and reassurance from leadership were left dissatisfied by a short agency-wide meeting about the shooting.

Chris Hosey, director of the Georgia Bureau of Investigation (GBI), said almost 500 shell casings were recovered. Of those rounds, about 200 struck facilities on the CDC campus.