Canterbury Metro Area Commander Superintendent Lane Todd said a driver failed to stop for officers when signalled to on Cranford St about 9am, and fled the scene.
Police opted not to pursue the vehicle, which shortly afterwards crashed into another vehicle at the intersection of Nancy Ave and Innes Rd, Mairehau.
An occupant of that vehicle received serious injuries and was taken to Christchurch Hospital.
Police arrested the offending driver - a 28-year-old man - and seized a firearm found in his vehicle.
The man sustained minor injuries in the crash.
Supt Todd said charges would be laid.
The road was closed while Serious Crash Unit conducted a scene examination, and inquiries are ongoing.
Anyone with information is asked to contact police: 105, event number P054933271.
