On 21 October 2002, at 11:24 a.m., Huan Yun "Allen" Xiang, a 36-year-old fourth-year commerce student, entered room E 659 of the Menzies Building on Monash University's Clayton campus during an econometrics tutorial attended by twelve students. Xiang climbed onto a desk and opened fire with a handgun, shouting "You never understand me!" while people in the room were initially confused by the noise and his behavior.
When Xiang paused to switch weapons, lecturer Lee Gordon-Brown — who had already been shot — grabbed his hands as he reached into his jacket. Gordon-Brown and student Alastair Boast then tackled Xiang. Bradley Thompson, who entered the room afterward, found five guns in holsters around Xiang's waist, including two Berettas, a Taurus, and two revolvers, along with two magazines. A passing lecturer, Brett Inder, helped Gordon-Brown and Boast restrain Xiang for roughly thirty minutes until police arrived, while Thompson and university administrator Colin Thornby administered first aid to the wounded.
Seven people were shot in total: two died and five were injured. The dead were Xu Hui "William" Wu, an international student from Hong Kong who was a neighbour of Xiang's in Melbourne, and Yat Ming "Steven" Chan, a student from Doncaster. The injured were Lee Gordon-Brown (arm and knee), Daniel Urbach (shoulder and arm), Laurie Brown (leg and abdomen), Christine Young (face), and Leigh Dat Huynh (leg, discharged within a day). After his arrest, Xiang, deemed unfit for interview, wrote a note stating "I finally ended WW's life," referring to Wu.
Xiang was charged with two counts of murder and five counts of attempted murder. At his two-day trial in June 2004, prosecutor Sue Pullen presented evidence that Xiang believed the killings were his destiny, that he had joined the Sporting Shooters Association of Australia in April 2002 and obtained a handgun licence in June 2002, and that he held delusional beliefs that William Wu was an "agent of evil" who would "destroy him academically." A lecturer, Gael M. Martin, testified she had raised concerns about Xiang's mental state a week before the shooting. Both defence and prosecution agreed Xiang suffered from a paranoid delusional disorder, and the prosecution asked the jury to acquit him. On 17 June 2004, a Victorian Supreme Court jury found Xiang not guilty of murder and attempted murder due to mental impairment. Justice Bernard Teague ordered his transfer to the Thomas Embling psychiatric hospital, where he could be held for up to 25 years.
On 20 October 2015, while detained at Thomas Embling Hospital, Xiang attacked a female consultant psychiatrist with a knife; in December 2016 he received an additional 7½ years in psychiatric custody for that attack.
Several people involved in stopping the shooting — Gordon-Brown, Boast, Inder, Thompson, Andrew Swann, and Thornby — received bravery awards, including Red Cross "Community Hero" recognitions, the Royal Humane Society's Stanhope Gold Medal and Clarke Gold Medal, and the Star of Courage. The shooting also prompted a review of Australian gun laws and subsequent handgun restrictions.