Racing at Northam Racecourse has been abandoned after a barrier attendant was reportedly struck by lightning at the track on Thursday afternoon.
WA Country Health Service confirmed the man, believed to be in his fifties, was in a critical condition following the incident.
Late on Thursday, he was transferred to hospital in Perth.
It is understood the barrier attendant, who lives in Northam and was a casual volunteer, had been working trackside at around 4.30pm near the 500m mark when he was struck.
Race caller Darren McAullay told Radio 6PR's Oliver Peterson the crowd at Northam Races the storm had "come from nowhere".
"We all jumped due to the noise. It was just so loud. I was looking just around the 200 metre mark," he said.
"I looked up further beyond the track and there was people waving. I looked through the... binoculars and a man was laying on the track with a sand bucket tipped over.
"I immediately saw he was in a fair bit of trouble.
"Ambulance staff hightailed it up to where the man was working... the paramedics were on the scene in about 50 seconds.
"They applied CPR and they also gave him mouth-to-mouth before the ambulance put him onto the gurney.
"It was only a very small crowd... it's just ended on a tragic note.
"There is absolute pool of gloom over the place at the moment."
Racing and Wagering Western Australia chief executive officer Richard Burt confirmed the Northam race track worker was taken to hospital.
"A Northam Race Club worker at today's Northam race meeting suffered a heart attack," he said.
"He has been taken by ambulance to hospital and is under medical care."