Hundreds of students gathered on the football field of a Calgary high school Thursday to grieve for a young player who died after injuring his head during the third practice of the year.

Tyler Zeer, a 16-year-old lineman with the Bowness High School's senior team, collapsed last Friday after smashing into a teammate in a routine drill. He remained in a coma until taken off life support Wednesday afternoon.

The school, which promised to review the accident, had crisis counselors on hand to console students and staff.

"What's happened at this school is the worst possible thing," said school principal Phil Tuck. "It's the worst possible fear for a parent, it's a devastating event."

It is not yet known what caused Zeer to collapse, after colliding mask to mask with a teammate. He was in good health and wore a helmet and full football gear.

"We've been told it was a good clean hit," said Christa Sutherland, a family friend.

"Tyler had played junior football last year, had been through this drill hundreds of times, so it's not like this was something brand new for him. It was just a freak accident."

Head injuries are common in sports, especially football. A recent study found that 20 per cent of high-school football players are likely to suffer concussions, compared to 10 per cent in hockey and 5 per cent in soccer.

However, the risk of a death like Zeer's is very low, said an expert in sports medicine.

"I don't want athletes and parents to become overly nervous or concerned that this is something that their child or they themselves are at significant risk to have occurring," said Dr. Scott Delaney, team doctor for the Montreal Alouettes football team.

"These deaths, however unfortunate, are usually rare and usually a handful occur across North America."

The funeral for another young football player took place in Kelowna yesterday. Jeff Halvorson, 21, collapsed last week during a running drill. The exact cause of his death is yet unknown.