Terror groups are like pedophiles: Shorten

Terrorist organisations are like pedophiles in the way they prey upon vulnerable young people, Opposition Leader Bill Shorten says.

His comment comes after reports the 15-year-old boy who shot dead a NSW police accountant on Friday had earlier attended a lecture by extremist group Hizb ut-Tahrir at the Parramatta mosque.

Farhad Jabar Khalil Mohammad was then shot and killed by special constables returning fire.

Mr Shorten wouldn't speculate on police investigations of the shooting or alleged extremist involvement on Monday, but said groups that filled the heads of vulnerable young people with "murderous crazy nonsense" were breaching their social contract with Australians.

"Labor has no time for any organisation found to be fomenting this dangerous, crazy rubbish, which is preying upon teenagers with such dreadful, tragic consequences," he told reporters in Sydney on Monday.

"These organisations preying upon young people are a sort of political or a terrorist version of pedophiles who prey upon young people."