A man has been arrested and charged with assaulting a Winnipeg Transit bus driver after he spat at the driver and the two traded blows on Wednesday.

The altercation took place Wednesday outside Polo Park.

Jeri Stern was riding the Route 21 bus around 4:30 p.m. when a dispute broke out.

"I heard some yelling and the passenger was swearing at the bus driver for some reason," he said.

Stern decided to pull out his cellphone and film the interaction.

"I just had a feeling it was the right thing to do," he said.

Stern's video captured the passenger spitting at the driver and leaving the bus, and the driver following the passenger and grabbing him.

The two exchanged a few blows before the video cut out. Stern said he stopped filming to call 911.

Winnipeg police said another transit driver and a civilian helped the driver restrain the passenger until officers arrived.

The suspect was arrested and assault charges were laid, police said.

"It was a clear case of a passenger assaulting a transit driver," police said.

Stern said he felt compelled to shoot the video because he empathized with the driver.

"I actually have a couple of close friends who work for Winnipeg Transit, and I know the kinds of stresses and the kinds of abuse they endure," he said.

While Stern did not catch what started the dispute, he believes the passenger provoked the driver by spitting on him.

No charges were laid against the bus driver.

There were approximately 60 assaults on transit operators in Winnipeg in 2015, Amalgamated Transit Union Local 1505 told CBC in January.

The most common time for assaults is around 4 p.m. and the vast majority of assaults begin with a fare dispute, said the union.