Farhad Khalil ­Mohammad Jabar would regularly skip school to pray at the Parramatta Mosque, less than 1km from the NSW Police State Crime Command building where he ­executed 58-year-old accountant Curtis Cheng on ­Friday afternoon.

Detectives searched the mosque on Saturday night after reports Jabar had been seen there before his attack, only hours after imams leading the day’s service included one associated with the controversial ­political group Hizb-ut-Tahrir.

Hizb-ut-Tahrir officials yesterday refused to condemn ­Friday’s killing during a public protest against the involvement of Western governments in the Middle East.

Like Islamic State, the org­anisation believes in the establishment of a “caliphate” or auto­nomous Muslim state and has been declared a terrorist ­organ­isation by other countries, ­although it does not endorse ­violence publicly.

One of the speakers at the rally, Hamzah Qureshi, said Hizb-ut-Tahrir would “stand with the Muslims of Syria”.

“The day is not far where we will witness a world where our children and our grandchildren will once again see the light of Islam as the world saw for centuries before,” he told the protest.

Responding to Friday’s killing, Prime Minister Malcolm Turnbull and NSW Premier Mike Baird held a teleconference with Muslim leaders on Saturday.

Yesterday, Foreign Min­ister Julie Bishop told the ABC’s ­Insiders program that families were Australia’s “frontline of ­defence against radicalised young people”.

“We’re certainly reaching out to the leaders of the Muslim community, but (also) working with the families at a grassroots local level,” she said.

Several of those involved in Saturday’s teleconference told The Australian they welcomed an apparent change of tone in the government’s ­response to the latest terrorist ­attack on home soil. Jabar, who was shot by police special constables, is thought to have been born in Iran, after his Kurdish family fled Saddam Hussein’s ­regime in Iraq, ­before moving to Australia several years ago.

He began to regularly attend Parramatta Mosque during the past two years, often praying there several times a day and staying late with a group of other young men. Several other teenage worshippers at the mosque are believed by authorities to ­privately support Islamic State, which has seized control of a large area of Syria and Iraq.

While these views are not ­endorsed by the mosque’s ­administration, several of its worshippers have also come to the attention of police involved in counter-terrorism operations in recent years. This revelation will raise questions over the handling of these worshippers by the mosque and law-enforcement officials.

A key part of the police investigation into Friday’s killing will be whether Jabar was radicalised solely through exposure to this group or through the influential online propaganda produced by Islamic State and its affiliates.

The group released an internet video in June apparently showing two of its fighters assassinating uniformed officials using an unprovoked pistol shot to the head — the same technique used by Jabar.

“It’s not something random that happened,” said Mofhu Sarani, a Sydney doctor who has been closely involved with the city’s Kurdish community since arriving as a refugee in 1992.

“He was in the mosque before the incident happened … unfortunately, now we hear of a lot of radical groups in different mosques — they use radicalism to target Western countries.

“The Australian security forces should find the group and work on the groups to stop these incidents … As the Kurdish community we are disappointed. We hope it never happens again.’’

Parramatta Mosque chairman Neil El-Kadomi condemned the killing. “We give our condolences to the (police employee) and his family. We will not say anything until the police investigation is finished,’’ he said.

Police do not believe Jabar knew or specifically targeted his victim, whose family yesterday released a statement saying that it was “deeply saddened and heartbroken that he has been taken from us’’.

The teenager’s shooting of Cheng is thought to have been opportunistically, Jabar possibly believing him to be one of the plainclothes police detectives employed at the State Crime Squad headquarters. “It could have been anyone walking out of the building and he’s come from behind and shot him. He would have looked like any one of us,” one police source said.

While Jabar had not previously come to the attention of police, it is understood a close family relation had contact with another Sydney man who has been charged with recruiting others to travel to fight in Syria.

Jabar’s sister is also being investigated after leaving Australia for Turkey a day before the shooting, with police considering the possibility she may have since travelled on to Syria or Iraq.

She is understood to have not left any message for her family explaining where she was going, and to have not been in contact with police since.

Another central question being pursued by the strikeforce investigating the killing is how a 15-year-old was able to get hold of the pistol used in the attack, although police have asked that details of this inquiry not be published for operational reasons.

An inquest into the most recent comparable attack in Sydney — December’s Lindt cafe siege — has heard the gun used was most likely bought on the black market and there is no record of it being imported into Australia.

Jabar’s family formally identified his body yesterday and repeatedly refused to talk to reporters.