It was a bizarre, senseless slaying of two unsuspecting loving parents by their mentally-ill son.

Crossbow killer Li Tian Jia said he “sent his parents to Heaven but that he would be in hell.”

Jia murdered his father, “George” Ji Jia, 59, with several bolts fired from a crossbow before luring his mother from her New Zealand home — where she cared for her dementia-ridden mom — to her death six days later.

Like her husband, “Shirley” Shi Zhou, 51, was killed with a crossbow while lying in bed. There were no signs of struggle in either murder.

Jia drew his mom home by saying that her husband won a lottery but was in a Buffalo hospital after a car accident, near Casino Niagara.

Jia then kept his parents’ corpses hidden in sealed bedrooms for almost two months while living as if nothing was amiss with other tenants there, said Crown attorney Phil Kotanen.

Jia, 31, was sentenced to life in prison Friday with no chance for parole for 22 years after pleading guilty to two counts of second-degree murder in the February 2013 killings.

The unemployed Jia suffered from a rare, severe form of obsessive compulsive disorder, which went untreated for years, said Kotanen.

He still collected rents, managed the house, bought groceries and seemed to be “unremarkable” to the tenants who lived in the house his father bought in June 2011 in the Pharmacy-Steeles area, court heard.

“While his mental illness is a significant factor these events,” Jia still understood the “moral and legal wrongfulness” of his actions, said Kotanen.

His actions were planned as he concealed the corpses for seven weeks before Jia confessed the double murder of his father, a semi-retired businessman, and his mother, a university professor, to a disbelieving cousin at their Huntsmill Cres. home on March 30, 2013.

During the confession, Jia also admitted he stabbed himself in the navel with a crossbow bolt because “I get sexually aroused by it, besides it’s also a ritual, my soul will leave this body from the same spot it entered.”

After the chilling revelation, the cousin offered to make Jia roast duck. She dodged out and phoned police from a pay phone in York region.

Jia left suicide notes, explaining the killings were part of a murder-suicide, court heard.

In Chinese notes he’d written for his cousin, he asked to die so he could avoid a life sentence, said Kotanen.

spazzano@postmedia.com