Police across the district are under a general arming order - meaning they are all carrying firearms - as a result of the incident.
The shooting comes just days after Christchurch man Kane Wayman - an associate of the Head Hunters gang - was killed.
Wayman had attended a New Year's Eve party at the headquarters of rival gang Mongols MC.
Four people have been charged with Wayman's murder and police have not ruled out further arrests.
"Two people who were with this man have been taken into custody and are assisting police with our inquiries," the spokeswoman said about the Kaiapoi incident.
"Those involved in this incident are believed to be known to each other and there is no risk to the wider community."
