Marion Adams died following the freak accident outside Rio Linda High School on Monday. (Facebook photo)

A popular California high school coach died after being impaled by a car-park barrier outside the stadium where he coached on Monday night.

Marion Adams, 59, a track and football coach at Rio Linda High School, Sacramento County, died in the freak accident while riding on his bike after practice.

He had turned to wave at a student outside the football grounds when he crashed into a partially open car-park barrier and was stabbed in the stomach by a pole.

Nearby students desperately tried to save him and kept him awake until emergency services arrived.

His son Joe Adams told CBS Sacramento: 'It’s like a nightmare. I keep waiting to wake up, just hasn’t hit me all the way.'

The coach was rushed to Mercy San Juan Hospital where he succumbed to his injuries.