Giuliano Pirone was working out in a Perth 24-hour gym when he felt unwell and made his way to a shower cubicle, where he collapsed early on August 20.
The 33-year-old's family raised the alarm about 3pm and police used the signal from the building supervisor's mobile phone to locate him.
Officers broke down the bathroom door and found the father of a young daughter slumped on the floor under cold running water about 10.30pm.
He never regained consciousness and died at Joondalup hospital about two weeks later.
WorkSafe WA confirmed on Tuesday that it was investigating the incident, including whether the gym breached its duty of care to Mr Pirone.
Doctors believe Mr Pirone's blood sugar levels became extremely low and his blood pressure dropped, potentially triggering a seizure, his family previously told ABC Radio.
Mr Pirone's mother Daniela Pirone said CCTV footage showed her son on a treadmill "not feeling too good" before bumping into other equipment in the gym.
"He staggers to the showers, holding his stomach," she said.
"[He] must have just locked himself in, felt hot, turned the cold water on and bang, he collapsed."
Ms Pirone said her family wants to know how her son would spend 15 hours in the shower without gym staff noticing.
The family has called for an inquest into his death to investigate whether the fitness industry needs tougher regulations.
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