A Toronto doctor who jumped in front of a subway train while cradling her baby son died of her injuries Saturday night. She had been in hospital for nine days.

Suzanne Killinger-Johnson, 37, leapt in front of a moving train with her sleeping child around 7 a.m. Aug. 11.

The six-month-old boy, Cuyler, died instantly.

Killinger-Johnson survived, but spent the past week in intensive care with severe internal injuries.

"Dr. Killinger-Johnson died peacefully at 8:30 (p.m.)," confirmed Sandra Cruickshanks, head of public affairs at Sunnybrook Health Sciences Centre, early Sunday morning.

"The family wishes total privacy on this," she added. "That is all they want me to release."

Experts believed she may have been suffering from the most serious type of postpartum depression, which can drive mothers to kill their children in a demented act of love.

It's believed the psychotherapist had considered killing herself and her son the day before the tragic jump.

Transit authorities had spotted her wandering along two different subway platforms, acting suspiciously. Security escorted her away the first time.

On the second occasion, police said they drove her home and left her in the care of relatives.

During Friday morning rush hour, Killinger-Johnson drove a silver Mercedes sports utility vehicle to the St. Clair West station. Horrified passengers watched as she jumped in front of a moving train.

It's believed she had stopped taking anti-depressant drugs because she was worried the medication might harm her son, who was breast-feeding.

Her mother, psychologist Dr. Barbara Killinger, has written books on stress, depression, and anxiety. Her father is also a doctor.