James Gargasoulas was a 26-year-old heavy drug user with an extensive criminal record when he drove a car at high speed through central Melbourne killing six people, including a baby boy and a 10-year-old girl.

He was sentenced to life in prison earlier this year for the January 2017 attack. Despite a guilty verdict there are still outstanding questions about why James Gargasoulas was able to carry out such a crime.

Four Corners investigates how James Gargasoulas was out roaming the suburbs of Melbourne despite facing serious criminal charges and clear warning signs that he presented a grave danger to others.

Australia boasts a stunning array of unique wildlife. They feature on our coat of arms and they're placed front and centre in our tourism campaigns. But the reality is, many of our native animals are in danger.

Australia has one of the worst extinction rates on the planet and the problem is growing. There are currently more than 500 animal species under threat.

Four Corners investigates how Australia has found itself in the midst of an extinction crisis.