TORONTO - Zhou "Peter" Fang and his mother Nora Fang suffered graphic abuse and degradation that is too obscene and depraved for any Hollywood script.

"William" Si Cheng tormented his son Peter since he was a crying one-month-old baby until the then 24-year-old killed him in a crowded Toronto public library in December 2010, a Toronto court heard Wednesday.

Peter pleaded guilty to second-degree murder in the Dec. 2, 2010 death of his father.

Peter was arrested after William, 51, was shot with a crossbow inside a public library in Toronto.

It was reported at the time Fang feared he and his mom would be killed if his father found them living in Ottawa. William was living in Toronto.

Senior forensic psychiatrist Dr. Hy Bloom described the Fangs' abuse case as "one of the worst and most chronic child and spousal abuse scenarios he has ever encountered."

Fang was pinched on the cheek as a one-month-old and when his mom intervened, Cheng attacked her. Later, he poured urine on to his son, forced him to eat vomit and fish from the garbage and he choked the child in his sleep.

The father twisted the heads off Peter's pet birds "as punishment for his son making a charitable donation at school," Peter Fang's lawyer Mark Sandler said.

He outlined 22 pages of "the most extreme, physical, emotional abuse" heaped upon both Peter and his mom.

Cheng threatened to kill or cut out his wife's and son's tongues -- and he chopped off a rabbit's tongue in their presence to emphasize the point -- if they divulged their torturous lives, Sandler said.

Both of them were sexually abused by the twisted Cheng.

The wife was so viciously beaten by Cheng that she stopped working as a teacher. Nora was temporarily blinded by the attack at the hands of her abusive husband, the documents indicate.

"I stopped working because of the cruelty I suffered at the hands of William Cheng," 51-year-old Nora wrote. "I was forced into hiding by Cheng."

Cheng and Nora's 17-year marriage -- which featured abuse dating back to their days in China -- collapsed after the May 2002 assault.

When Peter was 10, the family moved to Australia, but the abuse that marred their time in Canada never stopped.

Peter and his mom were beaten without reason, and the son was confined to a bedroom, forced to urinate in a bottle. Then the father poured the waste on to his son's head. When the mother was being sexually assaulted, the young son tried to save her but Cheng choked him.

The family moved to Vancouver in 1997 where Peter was choked in his sleep. His father was charged but the family moved to Australia before the courts dealt with the case.

They returned to Toronto in 1998 where Peter was ordered to sleep on a board and urinate in a bowl on the floor at night.

Cheng was repeatedly charged, convicted, given minor sentences and intimidated his hostage family members to convince authorities that he "had changed," court heard.

Peter still suffers from chronic post traumatic stress disorder but a psychiatric assessment indicated he's "not predisposed to violence towards others" or criminal behaviour in general.

Peter will be sentenced Sept. 4.