Zhou Fang confessed to firing a crossbow bolt into his father's back at the Main Street public library branch on Dec. 2, 2010, then crushing his skull with a hammer.
Fang, who is now 26, was initially charged with first-degree-murder in the death of 52-year-old Si Cheng.
But the prosecution accepted a plea of second-degree murder after considering that Fang was the victim of long-term abuse at the hands of his father.
The incident happened during the afternoon when the library was packed with children and other patrons.
Fang, who had been living in Ottawa, was arrested blocks away from the library.
Court heard that Fang was the victim of deprivation, beatings and psychological torture from the time he was a baby. A senior forensic psychiatrist who assessed Fang described the abuse as one of the worst child abuse cases he had ever seen.
Cheng had two domestic violence convictions involving his family, and a divorce lawyer for Fang's mother said both she and her son lived in fear of Cheng.
They had obtained a restraining order against him, and even went into hiding after the couple separated in 2002, the lawyer said.
(CFRB, The Canadian Press)