A fourth teenager has been charged after a senior police officer was assaulted and mugged on Sydney's northern beaches.
Police were called to Warriewood McDonald's after reports of a large group was causing a disturbance inside on Friday night, NSW Police said in a statement on Sunday.
After they ushered the group outside, police say a chief inspector, who was attempting to move on five teenagers, was knocked to the ground and had his mobile phone and badge stolen.
The group fled on foot with police, including the dog unit, launching a search in the area.
Two 16-year-old boys and a 17-year-old boy were later charged with a range of offences including affray and resisting or hindering a police officer.
They remain before the courts.
Police later arrested a 16-year-old boy at a Narrabeen home on Saturday night and he was charged with assaulting a police officer in the execution of duty, affray, and resist or hinder police officer in the execution of duty.
He was refused bail to appear at a children's court later on Sunday.
NSW Premier Gladys Berejiklian told reporters in Sydney on Sunday that she was "very concerned" to hear about the alleged incident.
She added that her government is considering what it can further do to prevent such incidents from happening.
Assistant Commissioner Mark Jones described it as a "vicious attack" on the police officer.