A four-year-old boy thought his mum was asleep after he saw her fatally hit her head while getting off a treadmill.
Shari Fietje's son, Astin, was reportedly watching his mum running when she fell over in the shed at their family home on December 3.
Jamie Fietje, from Auckland, New Zealand, announced the death of his 29-year-old wife on Facebook , describing her as the 'love of my life'.
In the heartbreaking post, he said Astin told him: "Mum was on the treadmill and got off and turned it off.
“Then she fell over and hit her head and went to sleep, so I went to sleep with her.”
Mr Fietje believes Shari suffered a medical episode on the running machine, although he was is still waiting for the coroner's official report.
He does not believe she died from tripping over and hitting her head, according to the New Zealand Herald .
He added: "It was so hard to hear this from Astin. I cannot comprehend why and am in complete disbelief this happened.
"But nevertheless, it caused Shari to pass away at only 29."
The grieving husband said it would be difficult to watch his children grow up without a mum.
Despite their mother's death, he added that Astin and his other son, Axell, one, are doing well/
Mrs Fietje was just getting back into running after undergoing a nose reconstruction operation.
She had previously completed a 10km run in Tauranga, with Mr Fietje sharing a picture of the pair after the race.
