A tall spruce tree in Marilyn Gunn's front yard was all that prevented a large yellow school bus from crashing through her front window Thursday.
The school bus that had been carrying about three dozen elementary school children to morning classes smashed into the evergreen after rear-ending a minivan.
"All of a sudden I saw this tree ... shaking violently and coming toward the house and then I heard the big crash," Gunn told The Canadian Press. "I got up and stood here in the window and I saw the school bus in the tree. I ran out immediately and heard the children crying inside and screaming," she said.
"Then our neighbour came out. We were trying to get the kids to open the back door and they couldn't, so we went out and got a crowbar. Then we helped the children across the street and sat them on the lawn and then went and got blankets. It was quite the morning."
Seventeen children, between the ages of five and 10, were taken to hospital with minor cuts and bruises.
The minivan had been turning left in front of Gunn's home on a quiet residential street in northwest Calgary when it was hit. The vehicle rolled through her yard and flipped over against a retaining wall on the driveway.
The drivers, both women in their 30s, had non-life-threatening injuries, police and emergency officials said.
Bill Russnak, still wearing his pyjama bottoms and holding a cup of coffee, didn't see the accident, but he certainly heard it.
"It was loud. It was as if you took two of those big garbage buckets and dropped one on top of the other at about 50 miles per hour," he said.
Russnak managed to get the rear door of the bus open so the kids could get out.
"The door would not open. We tried with our fingers. We got the crowbar, got the door pried open and started taking the kids out," he recounted.
"When we opened the door, it was a great feeling because they had relief and they weren't trapped anymore. Each one of them walked off the bus."
The children were understandably upset, said Gunn.
"They were scared. They were all crying and they were panicking. It was the most heart-wrenching sound. When you hear children screaming, your heart just melts. Especially as a mom and a grandma."
Police Insp. Curtis Olson said the outcome could have been a lot worse.
"They were all transported to the children's hospital. They are all in fine condition. There was minor bumps and bruising, but they have all been accounted for and are with their parents."
The cause of the accident was still under investigation, but there was a suggestion the brakes on the bus may have failed as it came down the hill to the corner where the collision occurred.
"Was it a matter of vehicle malfunction or was there some driver error? We can't say for sure right now," Olson said. "We're most concerned about the ... safety of the children and the safety of the community.
"What we will be doing at this point is assessing all the damage and determining what did take place and why it occurred."
Speed may have also been a factor, but alcohol was not, he added.
First Student Canada, the company that owns the bus, was also investigating.