He killed dozens of people in the Labor Party... but guess what?!? It's the Labor Party's policies that made the maximum possible prison sentence 21 years... Is that ironic or what?
he planed to be killed during the attack though, said he planned it as a suicide attack,
he will never be let out, they can keep anyone for life if they deem the person as high risk,
he can also be declared insane and be under psychiatric care for life