Prime Minister Malcolm Turnbull has urged parents to keep tabs on what their children are up, to head off the risk of exposure to terrorist groups like Islamic State.
Mr Turnbull said it's too early to say whether Parramatta police shooter Farhad Jabar Khalil Mohammad was a "lone-wolf" - someone who carries out violent acts of terrorism outside of a group command structure.
"We all need to be aware of the way in which radicalisation can occur - communities at every level, families should be aware of what young people are doing, what influences are impacting on young people," he told reporters in regional Victoria on Monday.
Investigations into Friday's shooting death of a police accountant by Mohammad are continuing.
Mr Turnbull plans to speak on Monday with the family of worker Curtis Cheng.
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"It's troubling and shocking that somebody as young as 15 would commit a crime like this - it is a doubly shocking crime for that reason," he said.
The prime minister said the internet was rapidly changing the dynamics of countering extremism, suggesting the government could learn from UK's experience.
"We have to constantly calibrate our response and learn from what we're doing, what works."
