Cynthia Wachenhem had left a 13-page handwritten suicide note before she jumped from the 8th floor of her apartment.
The 44-year-old lawyer had described her final act as "evil" in her notes. She was an attorney on leave with the Manhattan Supreme Court.
Wachenham believed her 10-month old son Keston suffered from cerebral palsy or some sort of neurological disorder after suffering two falls. She reportedly blamed herself for the falls despite doctors finding nothing wrong with it.
The suicide not was found under Wachenheim's bed, stating that she knew her action would be "evil," but that she was worried about her child's development.
Wachenheim was married with an only child. In her notes, she expressed "deep love for her son" and that she expected people to assume that she was a victim of postpartum psychosis, a symptom which could drive mothers to harm themselves and their children.
According to surveillance cameras, Wachenheim's husband had left the West Harlem apartment about an hour before the woman made the plunge. The window was open with no safety bars.
Yahoo reported that West Harlem resident Steven Dominguez witnessed the fall - the 18-year old was walking to the grocery store with his mother when the incident took place. He said the baby bounced off the woman's body, which probably broke some impact of the fall, before hitting the ground.
"I heard a scream like a yell," Dominguez said, according to the report. "When I got closer, I saw the baby crying."
He said the baby was face down.
"I was shocked," he said. "I couldn't believe it."
Resident Yaa Dwamena, 32, a fellow neighbor, lived in Wachenheim's building said she'd known the woman for several years, saying she was "nice, friendly," and "very warm."
Dwamena saw her neighbor just last week and didn't suspect any suspicious behavior.
"I wouldn't have thought anything was wrong with her," she said. "They were a happy-looking family. I wouldn't think anything like this would happen."
Wachenheim was a law school student at Columbia University. She worked in state Supreme Court in Manhattan doing legal research for judges, court officials said.