A search of Vitkovic's room after the killings revealed that Vitkovic kept press clippings of the Clifton Hill massacre, with extracts underlined in red. Police believed he had always intended to shoot people in the Queen Street building. It was reported that Vitkovic had left a note at his home; police indicated that it was not a suicide note. Vitkovic had obtained a shooter's licence and had bought the gun a few weeks before the shooting. He had illegally modified the .30 M1 carbine, by reducing the barrel's length. It was loaded with jacketed ammunition.