2nd LD: Australian PM says Sydney shooting "act of terrorism"

The shooting of a civilian police employee in western Sydney by a 15-year-old gunman was an "act of terrorism," Australian authorities said on Saturday.

"This appears to have been an act of politically motivated violence so at this stage it appears to have been an act of terrorism," Australian Prime Minister Malcolm Turnbull told reporters in Melbourne. "It is a shocking crime. It is a cold- blooded murder."

The teenager of Iraqi-Kurdish decent, born in Iran, shot and killed Cutris Cheng, a 17-year veteran in the New South Wales Police's financial department, on Friday afternoon.

"We're a long way from establishing a full picture of this man, and his exact motivations still remain a mystery to us," New South Wales police commissioner Andrew Scipione said.

Initial investigations by Australian counter-terrorism authorities indicated the teenage gunman was a "clean skin" - not on authorities radar of those suspected to be inclined toward terrorism, The Guardian Australia reported.

"We are exploring every avenue with regard to why he did what he did," Scipione said.

New South Wales Premier Mike Baird told reporters that the shooting would "echo around the world, as people try and understand how someone so young could commit such a hideous crime. "

"We cannot let actions such as this divide us. We cannot let hate overtake us," Baird said.

Turnbull echoed Baird's sentiment, urging Australians to go " about their day" on Australia's "grand final weekend," where the champions are decided for two of Australia's most popular sports - football and rugby.

"We have challenges, terrorism is one of them. But they must never divert us from our commitment to being free Australians, working together to ensure we achieve our common goals," Turnbull said.

The prime minister said it was important to remember the Australian Muslim community would also be shocked and appalled by the "act of terrorism."

"We must not vilify or blame the entire Muslim community for the actions of what is, in truth, a very, very small percentage of violent extremist individuals," he said.

The state and federal agencies were working closely together to seamlessly to ensure Australia's security, Turnbull said.

In December 2014, Iranian-born extremist Man Haron Monis and two hostages were killed following a 17-hour siege at a cafe in downtown Sydney. Endi