Witness accounts and police reports from the Darwin shooting suggest that the accused gunman was not only using an illegal weapon, but should not have been entitled to have access to any firearms at all, says Australia’s leading gun law researcher.

The alleged shooter is arrested in Darwin.

But this is not to say that gun laws failed, says Associate Professor Philip Alpers, the director of GunPolicy.org at the University of Sydney’s school of public health, which tracks and compares gun laws in jurisdictions around the world.

Reports suggest the gunman opened fire with a shotgun and was able to fire multiple rounds in rapid succession. Northern Territory police commissioner Reece Kershaw said the firearm, which was illegal, was possibly stolen as long ago as 1997.

Professor Alpers says this suggests he was either using a semi-automatic shotgun, which would be illegal under the national firearms agreement signed by the states and territories after the Port Arthur massacre, or a high-capacity magazine, which would also be illegal.