TORONTO -- A Toronto woman has been found not criminally responsible for the fatal stabbing of a complete stranger after a judge ruled she did not have the mental capacity at the time to know her actions were wrong.

Justice John McMahon said Tuesday that Rohinie Bisesar, who pleaded not guilty to first-degree murder in the death of Rosemarie Junor, was seriously ill during the attack in December 2015.

"I am satisfied on a balance of probabilities that Rohinie Bisesar suffered from a mental disorder, schizophrenia, when she took this woman's life," McMahon said. "Because of the schizophrenia, she was incapable of knowing the killing was morally and legally wrong."

Junor, 28, died after Bisesar stabbed her in the chest at a Shoppers Drug Mart in Toronto's financial district. Investigators found no prior link between the two women.

"This tragic stabbing of an innocent young woman can only be described as a senseless and motiveless killing," McMahon said as Junor's mother and husband cried inside the packed courtroom. "The bizarre nature of this killing makes no sense on rationale thought."

Bisesar, 43, sat in silence throughout the proceedings.

McMahon said she will now be sent to a secure wing of a mental health hospital in Toronto until she has a hearing with the Ontario Review Board, which decides if and how not criminally responsible patients should be detained.

Both Crown and defence lawyers had asked the judge to find Bisesar not criminally responsible in Junor's death.

A forensic psychiatrist who was the only witness to testify at the one-day trial last week concluded Bisesar was in the throes of a psychiatric breakdown due to untreated schizophrenia at the time of the attack.

Court heard that a second psychiatrist agreed with that assessment and both reported that Bisesar suffered from severe hallucinations and delusions that manifested as a voice commanding her to harm someone.

The stabbing -- which was captured entirely on surveillance video -- took place on Dec. 11, 2015, when Junor, an ultrasound technician, was at the drug store during a break from work.

The trial heard that Bisesar walked into the store just before 3 p.m. and went straight up to Junor.

"In those 54 seconds, the accused made her way into the store ... and inexplicably plunged the knife into Rosemarie Junor's heart," McMahon said.

Bisesar then placed the knife on a counter and walked out of the store, court heard.

Junor was rushed to a hospital, where she died four days later. That same day, police arrested Bisesar.

Bisesar's trial heard that she didn't initially believe Junor was dead, saying she was in hiding.

Dr. Ian Swayze, the forensic psychiatrist who testified, said Bisesar believed she was being controlled through "nanotechnology" devices in her body. She also told Swayze someone had "hijacked" her body and carried out the stabbing, he testified.

Last week, Junor's family had expressed anger at the prosecution and defence lawyers calling for a not criminally responsible finding.