Police on Tuesday morning have arrested and charged a student on his way to Arthur Phillip High School, the same school attended by the teen gunman behind last week's fatal shooting in Parramatta.

The student claimed that he was arrested because he was using his mobile phone to film officers who were positioned outside the school, as classes returned for the first time since Friday afternoon's shooting outside the NSW Police headquarters.

However, police said that officers had spoken to the teenager at about 8.30am in relation to alleged posts he had made on social media.

Fairfax Media has seen a number of posts on the teenager's Facebook account following Friday afternoon's attack on the police headquarters.

The teen posted footage of Commissioner Andrew Scipione's press conference and commented: "Bahahja f**k you motherf**ker Yallah merryland police station is next hope they all burn in hell."

Facebook post allegedly made by the student arrested outside Arthur Phillip High School on Tuesday.

He also posted footage of the news breaking of the shooting on Friday, commenting: "Serves you right I hope them lil piggies get shot."

Facebook post allegedly made by the student arrested outside Arthur Phillip High School on Tuesday.

The next day he posted a photo of himself with the comment: "No justice, no peace, f**k the police."

Police said when they spoke to the teenager on Tuesday morning, the teenager allegedly "threatened and intimidated police".

"He was arrested and has been taken to Parramatta Police Station."

The student was handcuffed and his belongings were emptied onto the footpath before he was taken away in a police van, the ABC said.

Police alleged that the teenager threatened and intimidated police during an altercation.

The teenager was charged with assaulting and intimidating police, two counts of resisting arrest and using a carriage service to menace/harass/offend after spending more than nine hours in police custody.

He has been given strict conditional bail and is expected to appear at a children's court on November 9.

On Friday, Farhad Khalil Mohammad Jabar, 15, walked up behind NSW Police accountant Curtis Cheng outside the police headquarters and shot him in the back of the head.

Farhad, from North Parramatta, was captured on video waving a gun above his head before special constables emerged from police headquarters and shot him on the footpath.

Farhad Jabar Khalil Mohammad, 15, who shot and killed Curtis Cheng on Friday. Photo: Instagram

He had been living with family at a North Parramatta apartment block and attending Arthur Phillip High School, just 300 metres from where he would carry out the attack.

Two detectives visited the Macquarie St school on Monday morning while several others returned to the area around the Parramatta Mosque.

A whole school assembly was held on Tuesday morning where students were offered counselling and urged to contact police or teachers with any information.

One student said many fellow classmates were visibly affected by last week's tragedy.

"They offered us counselling and they told us that if someone is facing problems, any type of issues, they can contact the teachers," she said.

"A lot of people had affected him in a way obviously...you wouldn't expect someone to turn out like that."

The senior student said she recognised Jabar from playing soccer after school but described him as a quiet boy.