A timber cross memorial to the 35 people killed in the 1996 Port Arthur massacre (Image: AAP/Robyn Grace)

As soon as Australia found out about the horrors committed at Port Arthur in 1996, whispers started that something was amiss about the official account of how Martin Bryant killed 35 people.

These conspiracy theories that someone else was responsible or helped carry out the massacre are patently untrue.

Bryant, who was known for killing animals and riddling their bodies with bullets, was the one who fired indiscriminately into a cafe, gift shop, a car and a bus at point blank range with an AR-15. There is no credible evidence that suggests otherwise.