With a gun pointed in his face, a security guard swung a bag containing about $200,000 into an armoured vehicle yesterday, leaving the would-be thieves empty-handed.

About 1.45pm two hooded men ran up to an ACM security guard moving money from the Westpac bank branch on Dominion Rd in Auckland's Mt Eden and threatened him with a shotgun.

A witness said instead of handing over the money, the guard threw it into the hold in his armoured car.

"He was either very brave or very stupid," the witness said.

"It was very heroic - he could have had his face blown off."

The amount the security guard was moving has not been confirmed, but it's believed to be as much as $200,000.

The hooded men fled in a black 4WD south down Dominion Rd. A third man is believed to have waited in a parked car nearby and acted as a getaway driver.

The vehicle was discovered to be stolen and was found abandoned.

The offenders were wearing dark hoodies, jeans and sneakers.

The witness said the security guard seemed remarkably unshaken by the incident. He told people at the scene it was the first time anyone had tried to rob him. "But he seemed completely all right."

Auckland police wanted anyone with information to contact them on (09) 302 6400.