Both left the scene immediately afterward, but later went to hospital with serious injuries.
Free said police had spoken to both of those involved.
“Through the course of our inquiries we are aware that several members of the public saw the incident and stopped in the bus lane.
“We need those people to contact us to assist the investigation.”
Anyone with dashcam footage of the initial incident or the assault should also contact police on 105 or go online to https://www.police.govt.nz/use-105 using ‘Update My Report’ and quoting the file number 240722/0952.