SYDNEY, N.S. -- An 18-year-old who died after he was hit by a school bus outside a high school last winter in Sydney, N.S., was pushed and fell over a snowbank into the path of the vehicle, a teenager testified Tuesday at another boy's trial for criminal negligence causing death.

The boy was the first witness to testify at the trial of the 15-year-old on what happened before the incident on Feb. 11 outside Sydney Academy.

Asked by Crown attorney Mark Gouthro to explain what happened to Christopher Chafe, the boy replied: "He got pushed into a bus."

The boy, who cannot be named, said he was standing with a group of five others including Chafe and the defendant when the incident occurred on the sidewalk in front of the school around 2 p.m. that day.

He said he saw the defendant use both hands to push Chafe in the upper chest before he fell over a small snowbank and into the street.

He noticed a school bus at a four-way stop sign just up the street from where they were standing before seeing it again just as Chafe was pushed, he said.

When asked to describe the force of the push, he called it a "a good push, a decent push."

Under cross-examination by defence lawyer James Snow, the witness was asked if he remembered telling police after the incident that Chafe had said: "What happens if you guys push me in front of the bus?"

The youth said he couldn't recall what Chafe said and doesn't remember being interviewed by police.

He agreed the incident happened "very fast."

Earlier Tuesday on the first day of the trial, court heard emotional testimony from the driver of the bus who said he didn't know anything was wrong until someone banged on the door of his bus.

Donald MacLean, who broke down when asked the number of his school bus, said he had gone to Sydney Academy to pick up a handicapped student when he noticed a group of about six students standing on the sidewalk near the school.

MacLean said he passed them and then pulled over to the side of the road. That's when he was alerted that something had gone horribly wrong.

"Next thing I heard was a person knocking at the door, so I opened the door and he said to me you have just run over a kid," MacLean said.

"I couldn't believe it -- I couldn't have because there was nobody in front of me. There was nothing there and I couldn't understand how something like that could happen."

MacLean said he got out of the bus and went to the back of the vehicle where he saw a person lying on the road.

"At that point I knew that he was deceased," he said.

Lyon Kengis, a paramedic who attended to the student minutes later, said the youth had suffered fatal head injuries and was pronounced dead at the scene by his partner.

Cape Breton Regional Police charged the 15-year-old boy more than a week after the student's death.