Police are investigating whether the driver involved in a collision that killed a woman and a dog in Central Saanich was impaired when it happened.

The incident happened in the 7600-block of Central Saanich Road just after 7 p.m. Monday.

Police say the SUV was heading south when it crossed into the northbound lane and struck two women who were walking their dogs from behind.

A 51-year-old woman was killed at the scene while her sister, in her 40s, was taken to hospital with life-threatening injuries. One of the dogs was also killed.

"We know the driver crossed over the centre line and struck these pedestrians who were on the side of the road," said Central Saanich Police Chief Les Sylven. "Why that happened, that's exactly what we're here to find out."

The 26-year-old man driving the SUV was taken to hospital with minor injuries and is said to be cooperating with police.

Investigators are looking into whether mechanical or medical factors were at play, but say the driver's sobriety remains a key consideration.

"The sobriety of the driver, those are conditions that we're looking into probably more than anything else at this point," Sylven said.

Relatives of the driver who live near the crash site identified him as Tony Thomas Jr. and say he has already been released from hospital.

One family member told CTV News he was on the road when the SUV began to swerve over the centre line, and even tried yelling at the women to look out, but he was too late.

Police say in the immediate aftermath of the collision, many bystanders assisted police and first responders including an off-duty paramedic who was "instrumental" in helping the struck women with their injuries.

"Another big part of today is supporting the families of everyone involved in this tragedy, and including all the first responders and all the people who came to the scene to assist us."

Investigators now want to talk to anyone who witnessed the incident and hasn't yet spoken with them.

Those with information are asked to call police 250-652-4441 or make an anonymous call to Crime Stoppers at 1-800-222-8477.