From 28 – 29 April 1996 Martin Bryant killed 35 people and injured 23 more in a mass shooting which became known as the Port Arthur massacre , during which he used a Colt AR-15 and a .308 L1A1 SLR . It was one of the deadliest mass shootings in Australian history and resulted in the '' National Firearms Agreement '' which restricted the ownership of all self-loading rifles and shotguns . In addition , the Australian government initiated a mandatory Gun buyback program with the owners paid according to a table of valuations . 660,959 firearms were handed in through this program
Port Arthur massacre
Port Arthur massacre (Australia)
Colt AR-15