Police say the bullet exploded through the rear window of the Ford Expedition Saturday night west of Edmonton and lodged into the metal part of a rear bench seat where three girls were sitting.
All of the people inside the vehicle were shaken up but no one was injured.
RCMP say before the shot was fired the driver of the Ford had argued with the driver of a white Lincoln MKX SUV.
Investigators say they found spent shell casings in the area, perhaps from a handgun.
Police say they are looking for the driver of the Lincoln — a clean-cut man in his 20s.
"We are just fortunate that there was no loss of life here," Cpl. Colette Zazulak said Tuesday. "This is an attempted murder investigation and we are encouraging the public to come forward if they have any information."
Zazulak said this is an apparent case of extreme road rage and motorists should be wary of challenging someone who is driving aggressively.
"Try to get a licence plate and report it to police," she said. "Engaging someone could have some very dire consequences."