It happened on East 135th Street at around 8:30 a.m. Wednesday.
The alleged 35-year-old gunman was in an apparent domestic dispute with his girlfriend when his neighbor, identified as 41-year-old Jemina Garay, intervened.
The suspect then pulled a gun and opened fire, hitting Garay four times, in her left eye, back, abdomen, and buttocks.
She is listed in critical condition at Harlem Hospital.
A 9mm shell casing was recovered in the hallway of the apartment building.
"They had told me that someone had just gotten shot in the head, a woman," said Marisol Otero, a resident. "I got scared, I got paranoid. I'm like, oh my God, right here in the building. I was scared to come out but I have an appointment so I got to go. I heard gunshots, I heard something. I'm still scared. I'm like, how am I going to go outside?"
Neighbors told Eyewitness News reporter Sonia Rincon that Garay works for a local veterinarian and loves animals and also has three girls.
The gunman, who has a criminal history, ran from the scene. Police believe he is still armed.
The suspect's girlfriend was not injured. There were also children in both apartments at the time of the shooting. They were not hurt.
Neighbors say the suspect doesn't actually live with the girlfriend, who they say lives alone with a toddler.
They said that they thought the suspect's girlfriend should have dumped him a long time ago and that he didn't treat her well, but they were still surprised to hear that he would have a gun.
ALSO READ | Good Samaritan helps grandmother chase her stolen SUV with grandchild inside
Good Samaritan helps grandmother chase stolen car with baby inside
----------
* Get Eyewitness News Delivered
* More Manhattan news
* Send us a news tip
* Download the abc7NY app for breaking news alerts
* Follow us on YouTube