Ottawa's transit service has launched an investigation after a YouTube video on the weekend appeared to show a city bus driver delivering an expletive-filled tirade against an autistic passenger.

The 55-second cellphone video attracted hundreds of views and many angry comments.

Shot on the No. 96 bus from downtown Ottawa to Kanata, the video shows a young man in shorts standing near the driver. Out of view, another man, apparently the driver, yells at the passenger.

'If you can't maintain dignity when you're in a job, you shouldn't have that job.'— Shneay Horwood, OC Transpo rider

“Shut the f---k up!” the older man says to the passenger. “Shut your ignorant f---king cake-hole! Don't say another f---king word!"

The stream of abuse includes a physical threat against the rider.

“If you don't shut your f---king face I'm going to stick my fist in it!"

As the bus stops at the Eagleson Park and Ride, the young man wheels around and runs out the back door, saying "Sorry" as he goes.

The person who shot and posted the video says in his comments that the young man had been talking loudly into a cellphone before he walked to the front of the bus, seemingly enraging the driver.

Only 2 passengers on bus

The young man tried to tell the driver he has a mental illness, according to the man with the camera, who was the only other passenger on the bus.

The passenger, 20-year-old Matthew Taronno, later described himself as "mildly autistic."

Regular OC Transpo riders who watched the video on Sunday were shocked.

"That's unacceptable," Ashlee Burkholder said.

"If you can't maintain dignity when you're in a job, you shouldn't have that job," Shneay Horwood said.

Diane Deans, the chair of the city’s transit commission, suggested that driver outbursts are rare at OC Transpo.

“Ninety-nine per cent of our drivers act courteously to our customers every day,” Deans said. “It's the odd incident that creates the problem."

In a statement, OC Transpo chief Alain Mercier confirmed an investigation is underway and said "appropriate actions" will be taken.

"Customer relations is always a priority for us and we take this situation very seriously," said Mercier, who added that any action taken against the driver will be kept confidential.

It's not the first time an OC Transpo driver's behaviour has been videotaped, even on the downtown Ottawa-to-Kanata run. A YouTube video posted earlier this year showed a driver complaining about the smell of smoke on a passenger riding the bus to Kanata. The driver then lost his temper with a passenger who objected to his rudeness.

The latest video upset Ottawa Mayor Jim Watson, who tweeted: "Regarding OC Transpo video — like anyone I am very disturbed by what I have seen and heard and want to see a thorough investigation conducted."