Mike Menane says the driver came out of nowhere, blocked his car and then smashed a side window with his fist.
And it's at least the second serious road rage incident in Calgary in less than a week.
Menane says he was headed to work driving north on Deerfoot Trail just after 9:30 a.m. Wednesday.
"I cut over from the left lane to the right lane because I see my exit coming up. I had already missed the exit for Blackfoot Trail," Menane told CBC News.
"I was driving up Deerfoot Trail going to work, I see a guy come out of nowhere and starts tailing me. Starts riding hard up on me. I tapped my brakes to let him know to give me some space."
Menane says he was under the exit lane overpass about to head westbound on Memorial Drive when the situation escalated.
"He cuts me off, I am trying to drive around him. He wouldn't let me. He comes to a stop on an angle. That's when I had to go in reverse to drive around the car. That's when he just ran up like a mad man."
And that's when the man struck Menane's rear driver's side window, smashing it with his bare fist, Menane said.
"He just comes up, literally just swings his hand, hit the window. It looks like he cut his hand pretty bad, too. There is some blood on there."
Menane says he's not angry, but maybe a little distraught.
"Anger is not going to do anything right now," he said.
"I am a little shaken up. I've got kids, my kids could have been with me. Driving to work and obviously I've got to deal with this now. You see this stuff happening, it makes you a little concerned. You just want to drive to where you got to go safely and with peace of mind, and you don't expect something like this to happen, right?"
Menane says he's filed a police report, including the licence plate of the silver Honda Accord, the other driver's vehicle.
CBC News contacted the Calgary Police Service, which confirmed Menane's general version of events, adding the other driver was located shortly after at a local hospital having his injury treated.
A police spokesperson says the other driver will receive a careless driving ticket, but no other charges will apply.
"In this case, the victim has declined that. But if the victim were to change their mind, then they could pursue criminal charges," the spokesperson said.
Police don't categorize reports as "road rage" so they aren't able to speak to a specific number of incidents or trends.
Last Thursday, two pickup trucks — one white, one black — were involved in an incident on Glenmore Trail, police said in a release at the time.
The drivers had a conflict that escalated, police say, and it's believed the driver of the white pickup intentionally drove into the back of the black pickup.
The white pickup then drove into oncoming traffic to get beside the other vehicle and forced it off the road by sideswiping it. Both were driving at an estimated 100 kilometres per hour.