Esmin Green had been waiting in the emergency room of King County Hospital in Brooklyn for nearly 24 hours when she toppled from her seat at 5:32 am on June 19 and fell face down on the floor.
She was dead by 6:35, when someone on the medical staff, flagged down by a person in the waiting room, finally approached and nudged Green with her foot.
Security guards and a member of the hospital's staff appeared to notice her prone body at least three times, but made no visible attempt to see if she needed help.
One guard, who did not leave his chair, rolled it around a corner to stare at the body and then rolled away a few moments later.
The video footage showed that other patients waiting nearby did not react.
The New York City Health and Hospitals Corporation, which runs the hospital, said six people have been fired as a result, including security personnel and members of the medical staff.
Alan Aviles, the corporation's president, said in a statement that officials will carry out "a thorough investigation to answer any questions that remain".
The psychiatric unit at the hospital had already been a subject of complaints by advocates for the mentally ill.