Really? I'm quite sure that this isn't true.

Is he a soldier? The Australians don't train soldiers to line people against walls for executions.
Also, why was he executing them? Execution implies some plan or accord.

He didn't send them to the wall. Inexplicably, they all went there on this own. One fellow stood facing the wall as if he couldn't hear the shots fired, and appears to be surprised and unaware.

The story presented is:

This Australian environmentalist travels around the world saying kind things, in Muslim, and European nations.
He then writes a racist manifesto, and massacres 50 people in a neighboring island country???
Initially, there were other agents, and bombs in multiple buildings, but that complicates things, so now it's one lone super warrior who listens to Serbian nationalistic music (ww1's Gavrilo Princip comes to mind); working alone and killing more people than Rambo.

What hasn't been mentioned is the fact that this sort of attack benefits Israeli interests. It's not surprising that it's ignored by the news, but surprising that it's ignored here.

This reeks of an Israeli operation.