Matt Strength says he was driving on Highway 97 near Summerland, B.C., at around midday Sunday when he saw the rock face fall in front of him.
The slide brought down tonnes of rocks and boulders, which covered four lanes of the highway.
"Kind of blows your mind seeing it happen right in front of you," said Strength, who is in B.C. on vacation.
"You could see the whole cliff face just sloughed away right from the side of the cliff and ended up going right into the road. So apart from the dust cloud afterwards, you have a pretty good view of everything happening."
Strength said he heard a car alarm go off and suspected that a vehicle was hit in the slide.
He ran through the dust cloud and pulled a man and a woman, both in their 60s, from inside a vehicle that was partially crushed by the debris.
"I wasn't really thinking about it; just wanted to make sure people were OK," he said.
Strength said both people had cuts to their faces and the woman was initially unconscious. The man was conscious but was moving with a limp, he added.
"Looked like he had a small cut on his forehead and a little bit of chest trauma and possibly a broken or twisted ankle," he said of the man.
"He was limping a little bit, but he was just making sure his wife was OK and concerned about her well-being."
Strength said he had to move rocks and debris away to get to the injured woman in the passenger seat. A doctor arrived soon after and helped Strength and another man remove the woman from the car.
The two injured people were taken to hospital in Penticton, B.C., with non-life-threatening injuries.
Strength said it's a good thing no one was more seriously injured in the rock slide.