A 19-year-old man who supplied the gun in a plot that led to the 2015 death of Sydney police accountant Curtis Cheng has pleaded guilty to committing a terrorist act.
Mr Cheng, 59, was shot at close range in the back of the head as he was leaving work at the NSW Police Headquarters in Parramatta on October 2 that year.
Raban Alou was one of four men who were accused of supplying the gun, a .38 Smith and Wesson, to Mr Cheng's killer, 15-year-old student Farhad Mohammed.
Alou has now admitted to supplying the gun.
After receiving the weapon from Alou at a Parramatta Mosque, Farhad Jabar went to Parramatta Police station and shot Mr Cheng dead.