WA Police Commissioner Chris Dawson speaks on Friday about the shooting near Margaret River. Credit:AAP

The slaying of seven people, including four children, near Margaret River in Western Australia is Australia's worst mass shooting since the Port Arthur massacre in 1996.

Police found seven bodies with gunshot wounds at the rural property on Friday morning, as well as two firearms. No one is being sought for the killings.

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The number of deaths considered to be a mass shooting can vary, however a recent study by University of Sydney and Macquarie University researchers regarded it as five people killed, not including the perpetrator.