A seventh victim, a female doctor, was found killed on the 17th floor of the hospital.
Henry Michael Bello, a 45-year-old family medicine doctor formerly employed at the hospital, according to sources.
A photo provided by authorities shows him dead on the floor, wearing the bloodied doctor's coat.
Bodo locked the door to the room, noting the other patient had some sort of a spine injury and was unable to get up from his bed.
"In the middle of a place that people associate with care and comfort, it came out of nowhere, but even in the midst of this horror, there were many, many acts of heroism," de Blasio said as he thanked police and first responders.