While Australia hypes up a war on Islamic terrorism, and New York City hypes up a police war on (not-so-) minority communities, there is another element that links the recent murders in Sydney and Brooklyn: Both gunmen had already exhibited violence against women.
The New York murderer of two policemen had that day already shot his ex-girlfriend in a town near Baltimore and had a history of violence (including to himself) and mental instability.
The Sydney murderer of two of the hostages that he held for 18 hours also had an established history of violence, including being an accessory to the brutal murder of his ex-wife a year and a half earlier. He was let out on bail. Two months ago, he was charged with 40 counts of sexual assault. He was again let out on bail.