Killen was unable to free himself from the sludge and was eventually pulled from the mud by his friend, Dave Grey, early on Tuesday morning.
Grey said he found Killen, with his head and shoulders out of the ground, metres from his bogged tractor.
“When he didn’t ring, I tried ringing him and I thought I would come and check him out,” Grey said.
“(He is) probably one of the toughest people I’ve seen at that age… even ambos and police were commenting on how resilient he is, a tough old bloke.”
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Killen was treated for hypothermia, dehydration and scrapes at the scene.
Emergency crews were stunned a man in his 90s could survive such an ordeal
He is currently in a serious condition at Sunshine Coast University Hospital.