Just what drove Peter Miles to commit the worst mass shooting since Port Arthur? It’s a question everyone has been asking since Miles murdered his family last month near the idyllic seaside town of Margaret River in Western Australia. He shot his four grandchildren, his daughter and his wife before turning the gun on himself. In this Sunday Night investigation, Aaron Cockman – the grieving father who lost his family in the massacre – finally answers that question. Denham Hitchcock has this report.