Four people are dead and a fifth person is in hospital after a suspected murder-suicide along a busy stretch of highway south of Calgary.

Two of the dead have been identified as Tanner Craswell, 21, and Mitch MacLean, 20, both from Prince Edward Island. The men, who attended the Canadian Prairie Baseball Academy in Lethbridge, were on their way home for the holidays.

The woman in hospital has been identified as Shayna Conway, also from Prince Edward Island.

RCMP Sgt. Patrick Webb said police found a car and SUV along Highway 2's northbound lanes, about one kilometre north of Claresholm, at about 3:30 a.m. Thursday.

Five people were with the vehicles. Three of those five people died at the scene from gunshot wounds, while a man and woman were taken to hospital.

The man later died from his wounds, leaving the woman as the only survivor.

Police said they hope Conway will be able to tell them how the victims were connected to the gunman.

"We believe that she is going to be able to provide us with a large amount of information about exactly what happened in the circumstances," Webb said.

It is not clear whether weapons were found at the scene on the four-lane, divided highway near the town of Claresholm, Alta., a community of 3,300 people.

Resident Brent Chimko told CTV News that he can't believe this kind of ugliness took place just outside his hometown.

"It's pretty shocking," Chimko said. "I've never seen anything like this."

Webb said the shooter was a man who gunned down the victims before turning the gun on himself.

Police found four of the people in one vehicle and the fifth person in the second vehicle.

Residents in the area say an altercation broke out at a local 7-11 store in Thursday's early hours, but police have not confirmed whether it has any relation to the grisly roadside scene.

Police towed away the two vehicles for further investigation later Thursday evening.

Highway 2, about an-hour-and-a-half south of Calgary, was closed four hours on Thursday in both directions.

Several secondary highways were also closed, impeding travel throughout the region.

With a report from CTV's Alberta Bureau Chief Janet Dirks and files from The Canadian Press