"John's a businessman in the magazine cover lamination industry, but he's also a hobby photographer with a love for speedway cars," Koh said.
Sprague has three adult children including a daughter who is a senior nurse, Koh said.
"All we know at this stage are what's been reported in the media," he said.
"But there's a lot of questions on what happened and why was he allowed to be in a position where the car could hit him."
Worksafe says it has been notified of the incident.
"WorkSafe will make preliminary enquiries," a spokeswoman said this morning.
St John Ambulance were told of the incident by paramedics already at the speedway just before 8pm last night.
The man was taken to Auckland Hospital in a critical condition.
Police said in a statement that a worker at the speedway had been hit by a stock car, sustaining critical injuries.
Speedway president Frank Irvine last night said a photographer had been injured but was unsure what happened.
Irvine has been approached for further comments this morning, but has yet to respond to the Herald.
A witness said the man was taking photos and may have been standing too close to the track.
A man in the crowd, who did not want to be identified, told the Herald the photographer was in the infield area when he was struck by a stock car being driven by a longtime Waikaraka driver.
"The car came around the back straight and around the turn. The person standing there was obviously too close to the track and the car clipped him.
"He flew 10 metres and rolly-pollied and then stayed still ... the car was going full speed."
As others rushed to help, the driver emerged from his car, the man said.
"He put his hands on his head."
