The 14-year-old girl from Casino High School, who was sitting on the bus with about 20 others, sprung into action when she noticed it moving without anybody in the driver's seat, narrowly preventing what could have been a major disaster.
Shorter TLDR: Driver outside bus, no report of why, or why it was not secured. Girl on bus steers it away and hits brake while driver panics and tries to stop bus by holding on to and being dragged by the mirror.
From the article: "The incident has been reported to officers from Richmond Police District who have commenced an investigation."
If I was the driver's lawyer, I'd be instructing him to keep his mouth shut for the entirety of that investigation and whatever criminal charges might follow.
At the start of the video the bus is stopped on a downhill, so the handbrake must have been on. Did it fail or did a student release the brake? Whatever the answer, the driver failed to maintain proper control of the vehicle and and also failed to supervise the kids. A lot of people could have died and he's in big trouble.
The hill doesn't look particularly steep, and I think the bus was already rolling at the start of the video, seemingly from an even less steep section. I wonder (pure speculation here) if perhaps the bus was at first holding in place thanks to only the resistance provided by being in gear.
Article doesn't say she steered it. You say the driver was dragged by the mirror but to me it looks like the driver maybe pushed it away just enough to enter the driveway rather than go over the gutter.
You can see it veers suddenly when it reaches the driveway. The right wheel reaches it first so that would have made it veer right.
And if it did hit the gutter instead it would have slowed, maybe even stopping by the time the rear wheels hit.