A 16-year-old was one of four men to be arrested early Wednesday morning in joint counter-terror raids carried out by over 200 officers across Western Sydney.

The men are suspected to be related to the fatal shooting of police accountant Curtis Cheng, 58, outside the Parramatta police headquarters last Friday by teenager Farhad Jabar Khalil Mohammad. According to Deputy Commissioner Catherine Burn, the four men “may have some knowledge” of what is believed to be a terrorism offence.

The 16-year-old, who cannot be named, was reportedly a classmate of Farhad Jabar at Arthur Philip High School, while an 18-year-old man, also from Wentworthville, identified by reports as Raban Alou, is the younger brother of Kawa, who was arrested in last September’s Operation Abbeby raids but released without charge.

Former Arthur Philip High student Mustafa Dirani, 22, another target of last September’s raids, which targeted a group planning to publicly behead a citizen, was arrested in Marsfield. A 22-year-old from Merrylands was also taken into custody this morning.

All four have been taken to various police stations, and it is expected the search warrants will help police advance their case of the murder of Cheng in court.

“Today’s operations is a clear indication of our determination to actually find out who murdered Curtis Cheng,” said Burn.

“It’s a very, very serious concern that in the heart of our community, there is attack planning that is underway, and that may have led to what we saw on Friday.”

A 24-year-old man was also arrested at his Merrylands home this morning on unrelated fraud offences.

Connections with Farhad Jabar

The exact associations between the four men and Farhad Jabar and his family are still being established, although it is alleged that some of the four had been at the Parramatta mosque with Jabar on Friday before the 15-year-old walked to the Parramatta police HQ and killed Cheng at close range.

However, NSW police said that any substantive links cannot be established yet. It also noted that while two of the men were connected to counter-terrorism raids in September last year, Jabar was not someone they “would have assessed as a threat”.

“The 15-year-old deceased was not a target for us,” said Deputy Commissioner Burn. “We did not know of him before Friday.”

When questioned about how the public can be confident of police counter-terrorism efforts when a gunman was not even on their radar, Burn said the reality is that police teams cannot monitor “everyone, everywhere, all the time”.

“It’s an unfortunate sign of the environment that we are now in. We know that we are seeing people younger and younger being influenced…but we cannot be monitoring every single person…and that is the unfortunate reality.”

AFP Acting Deputy Commissioner Neil Gaughan added that blaming a team or officer is “fruitless”, and that the police would need to work with the community and the media to stem a “likely” terrorist attack.

Australia is currently on a high level of terrorism alert.

Gaughan also announced that police are in contact with Turkish authorities who are “actively” looking for Jabar’s sister, who had left Australia the day before her brother’s murder. There is however, nothing at the moment to suggest she was involved with her brother’s plans.

Wednesday morning's arrests came just after the home of a Guildford teenager, who allegedly threatened police on his Facebook page, was raided on Tuesday night. The Arther Phillip High student was stopped by police on his was to school and is due to appear at a children's court on Nov. 9.

Contact the writer at feedback@ibtimes.com.au, or let us know what you think below.