CALGARY -- Calgary police have release a composite sketch of a suspect and photo of a vehicle believed involved in a road rage assault in August that left a victim suffering serious stab wounds.

Two men were riding in a Black Mazda 3 just after 9 p.m. on Aug. 5 when police say a grey or silver SUV began tailgating them, so the driver pulled over in the 500 block of 10th Avenue N.E. — in the community of Renfrew — to let the other vehicle pass.

But police say the driver of the grey SUV also pulled over, got out of his vehicle and walked toward the driver side of the Mazda.

"He leaned in through the victim’s open window and stabbed the driver before leaving the scene," read a release.

The driver was taken to hospital in life-threatening condition and has since been released.

The suspect is described as being in his late 20s to early 30s, between 175 and 182 centimetres (5-9 to 6-0) tall, with a slim build. He was wearing a grey hoodie, red baseball cap, white sneakers and a surgical-style mask.

Investigators believe the attacked was unprovoked.

Anyone with information is asked to call police at 403-266-1234 or Crime Stoppers at 1-800-222-8477.