A third person has been charged after an off-duty police officer and a passenger were assaulted on a bus on Sydney's lower north shore.
Police say the 44-year-old got on the bus with a 40-year-old man and a 13-year-old girl at Drummoyne on Saturday afternoon.
A short time later one of the men allegedly attacked a 67-year-old male passenger.
The driver stopped the bus and the off-duty senior constable intervened but the trio started kicking and punching the officer before they ran away.
The officer was treated for swelling and facial cuts, while the passenger did not need treatment.
Police cordoned off the area and arrested the younger two on Saturday, but the older man was only arrested on Thursday morning.
He was charged with assaulting a police officer in the execution of duty occasioning actual bodily harm, common assault, and affray.
The man was refused bail to appear at Burwood Local Court on Friday.
The two others who were charged remain before the courts.