The shooting happened just before 1 a.m. inside a commercial building at 119 Broadway.
The victims were identified as 18-year-old Omani Free, a senior at Newburgh Free Academy, and 20-year-old Tabitha Cruz.
Imani Robinson says there was an argument at the DJ booth, the lights went off, and then bullets started to fly.
"Somebody grabbed me and threw me into one of the rooms in the corner, because there was like a room...like there was a door, and the opened it and was throwing people in there," Robinson said.
There was no back door in the space, and the front door was their only option.
Omani's mother says she is still in shock.
"I'm just hanging on, that's all I can do," said Rhonda Free. "She was a beautiful girl, my chocolate baby, she was a beautiful girl."
She said the party was organized by another local young person.
"It was a Halloween party, it was a teenage party, and she was trying to get out," said Rhonda. "She got shot, she fell on another girl that got shot and that's the way it was."
She said Omani decided at the last minute to go to the party.
The gunman fled the scene. Police are not sure whether they are looking for one shooter or multiple shooters.
The mother of one of the shooting victims believes that a few days ago, someone was passing out flyers for the party all over the campus.