The Austrian engineer was found guilty for locking up and raping his daughter Elisabeth in a cellar over 24 years, fathering seven children with her, and causing the death of his own infant son.
Albert Dubanovsky, who lived in Fritzl's Amstetten home for 12 years, said that he went to school with Elisabeth. He has now revealed that he was there on the day Fritzl incinerated the body of his two-day-old son.
Out of the seven children Fritzl fathered on Elisabeth, one, named Michael, died of breathing complications soon after birth.
Instead of getting medical help, Fritzl burnt the baby's body in the central heating furnace to dispose of him.
"There was a disgusting smell in the air. My friend, who was keen on barbecues, said it was like burning meat," the Daily star quoted Albert as saying.
And he thinks that although Fritzl claims to have soundproofed the cellar, he could hear Elisabeth's cries for help.
"I used to hear knocking on the walls and I asked him about it. He told me it was the new central heating system," he said.