The man was shot at 10.46am during an operation in Bishop Auckland, County Durham, and taken to hospital.
A spokeswoman for the force said: “The Independent Office for Police Conduct has been informed of the incident and Durham Constabulary will be supporting the IPOC investigation.”
No further details were given about the shooting or the man’s condition.
A witness said the man was shot through the passenger window of a taxi after it stopped at a temporary traffic light.
He said the man was given several warnings to get out of the vehicle with his hands up.
While officers shouted at the passenger, the taxi driver got out safely.
Even after he was shot once in the upper arm or shoulder, the passenger continued to shout at the police, the witness said.
He also tried to get off a stretcher as he was taken away by paramedics.
“The police were not pussyfooting around,” the witness said.
“They shouted, ‘This is your final warning, if you don’t get out we will shoot’.
More from County Durham
‘Corsa cannibals’ strip car of bonnet and lights
Snow baby Sienna born on side of busy A66 in freezing conditions
Girl, 14, arrested after boy splashed in face with chemicals at school
Fury as police shoot dead abandoned dog left alone in freezing cold
Lockdown at Durham police station after ‘historical explosives’ handed in
House on sale for £1 – but dare you step inside?
“He didn’t get out, and… bang.”
A white forensic tent has been erected at the scene of the shooting, and a police cordon has been set up close to the Masons Arms pub in the Etherley Dene area of Bishop Auckland.