Two of his recruits had posed for pictures with severed heads in Syria and Iraq.
But Australian Mohammad Ali Baryalei, 33, wanted to shock his countrymen even more.
On Tuesday, he made a chilling phone call - most likely from Syria where he is believed to be based - to a 22-year-old in Sydney.
He told Omarjan Azari to kidnap a stranger in Sydney's Central Business District, drag him on to the streets and then behead him before shocked passers-by. Omarjan was to film it and upload the video online.
Australian media reported that the police had intercepted a call between Omarjan and Baryalei, a one-time nightclub bouncer in Sydney's King Cross and a part-time actor.
Baryalei is alleged to have been the go-between for Sunni extremist group, the Islamic State in Iraq and Syria (also known as ISIS or ISIL) and Australian radicals.
The man is behind some of the most horrific acts carried out by the militants.
While in Syria, he recruited a number of Australians, including Sydneysider Khaled Sharrouf.
It was Khaled who had his young son pose with a severed head in Syria.
He also recruited Mohamed Elomar, a former boxer who was also photographed holding the decapitated heads of his "enemies".
Baryalei, a senior ISIL militant and one-time street preacher, is said to have recruited half of the 60 Australians fighting in Syria and Iraq.
The Age reported that Baryalei's family had fled from Afghanistan as refugees when he was a child.
Yesterday, about 800 police officers arrested Omarjan and 14 other people in predawn raids conducted in Sydney and Brisbane. The raids took place just days after Australia had raised its national terror threat level to high.
But there was no time to waste after the phone call.
Australian Prime Minister Tony Abbott did not name the suspects, but told reporters: "The exhortations, quite direct exhortations, were coming from an Australian who is apparently quite senior in ISIL to networks of support back in Australia to conduct demonstration killings here in this country."
Some of the raids took place in upper middle-class neighbourhoods in Sydney such as Bella Vista and Castle Hill.
A home in these suburbs can cost A$1 million (S$1.14 million).
"You read about these things happening overseas, but not in your own backyard," Castle Hill resident Jim Richardson told The New Paper.
Omarjan was charged in court yesterday and court papers revealed that Baryalei's orders were for Omarjan to carry out an attack "clearly designed to shock, horrify and terrify the community".
In court, the police described Omarjan as displaying "an unusual level of fanaticism" in the call he made to Baryalei.
Singapore-based terror analyst Rohan Gunaratna told The New Paper that such a level of fanaticism should not be surprising, given ISIS' preference for "shock tactics" as a way to assert control.
"ISIS uses brutality and violence with the intention of intimidating and numbing the masses," added Dr Gunaratna of Singapore's International Centre for Political Violence and Terrorism Research.
"Their shock tactics are designed to overwhelm and to influence their potential supporters and create a fear psychosis among their opponents."
An offshoot of Al-Qaeda, ISIS has, under its control, large swathes of Iraq and Syria. It has declared an Islamic "caliphate" in the region, committing widespread atrocities and instituting a brutal interpretation of Islamic law.
Laws and Syrian conflict
Several countries are examining laws that would prevent its citizens from leaving to join the Syrian conflict.
And Britain, which has the largest number of foreign recruits in ISIS' ranks, wants laws to prevent them from returning.
It also wants the power to revoke the citizenship of those who hold dual citizenship.
All this is in response to the Sunni extremist group's power in recruiting foreign fighters.
There are about 12,000 foreign fighters involved in the three-year-old Syrian conflict, which has now spilled over into Iraq.
Dr Rohan Gunaratna of Singapore's International Centre for Political Violence and Terrorism Research said ISIS "has attracted many radical Muslims who believe they are joining because they are answering a call by God, but this view is not shared by a majority of Muslims here."
ISIS had declared the establishment of a caliphate known as the Islamic State, with its leader Abu Bakr as the caliph.
It also declared that Muslims all around the world must pledge their allegiance to the new caliph. But the Internet has been a game changer too, with ISIS spreading its agenda online, especially via social media.
In an oral reply to Parliament on July 9, Deputy Prime Minister Teo Chee Hean said: "Youths, who are the primary users of social media, are particularly vulnerable to such propaganda.
"It is not possible to completely insulate Singaporeans from the radical rhetoric that is so prevalent online.
"Singaporeans therefore must play their part to prevent loved ones and friends from becoming radicalised and embarking on a path of violence and self-destruction."
Dr Gunaratna said foreigners who join ISIS now are unlike those who joined the fight in Afghanistan in the 1980s and 1990s.
Many of those combatants would bring back what they learnt to their home countries.
But those who join ISIS are joining "group terrorism and they will have an ideology that will compel them to carry out attacks anywhere in the world", added Dr Gunaratna.
A number of Singaporeans are in Syria, including a woman who joined her foreign husband and two teenage children.
DPM Teo told Parliament: "The whole family is taking part in the conflict in various ways, either joining the terrorist groups to fight, or providing aid and support to the fighters."
Several others who had intended to travel to Syria or other conflict zones to engage in the jihadist violence were intercepted.
DPM Teo had said: "We have established that they were radicalised by videos, articles and social media postings online.
"They subscribed to the sectarian-religious or ideological rhetoric that calls for engaging in militant jihad in Syria."
This article was first published on Sep 19, 2014.
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