The internet makes the issue of import/export definitions redundant,
I can link to a blog where readers post questions to an ISIS fighter in Raqqa and receive a reply almost in real time.
They're on Twitter, Snapchat, Instagram, Facebook, Kik and Youtube.
The IS magazine Dabiq comes out in most languages including English and is easily accessible via Google.
Jamal Rifi, the Grand Mufti Dr Ibrahim Abu Mohammed and all the other "community leaders" are irrelevant since the government is not in a position to support them or move against what are effectively now the Muslim mainstream and the idols of young Muslims all over the world.

Emperor Julian,

Well said, your Highness. The problem can only worsen with Turnbull mismanageing of the country. Not only did he chastise Abbott for not 'speaking nicely' about the problem, he has also bowed down to a self-apointed Muslim PR man, and dropped Abbott's idea of including only persecuted minorities like Christians in the 12,000 "Syrian" country shoppers to be foolishly let in here. As it has been reported from Europe that 75% of these are not even Syrians, we are in for a real barrel of laughs after they arrive

I think its fair to say there was at least some Islamic extremist influence in this event.
Other than that I wouldn't jump to any conclusions until we find out whether or not he was on any prescription drugs at the time.
Then I want to know where he got the gun.
And does anyone know : Did he single this guy out?

Butch,
If the government was genuine in their concern for the welfare of Aus citizens, they would stop further entry of muslims immediately, whether they be immigrants or refugees.

The experts tell us that 15-25% of muslims have extremist views which is far too high for security reasons.

They are taught radical views from the cradle, for example take that well publicized picture of the little boy holding up a severed head. Then the pic of a mother with a baby in a pram holding a sign saying 'Behead those that insult Islam'.

Today there is a facebook page praising the Parramatta murderer.

Banjo, why discriminate against all muslims because of the attitudes of a minority of them?

It's not as if that minority are hard to weed out: all potential immigrants (regardless of religion) should be barred from entry if they don't support freedom of religion (including freedom to change religion) for everyone.

Aidan,
Simple answer, they'll lie. The very nature of reality differs between people from the West and people from the East.
ISIS and similar groups call their adherents "reverts", not converts, that is to say the view is that being a Muslim is an essential personal quality which people can either choose to ignore or embrace.
See this is why we say "Yes all Muslims" because this is the way Asian people think, they themselves say "All Muslims" and people from the West can either ignore the fact that Islam was built from the ground up to suit the Eastern Psyche or accept that even after three generations of co existence their way of life and their way of thinking is still totally and irredeemably different to ours.