Police say 21-year-old Rayquan Williams was arrested Thursday night.
He faces charges of criminal sex act, robbery, sex abuse, attempted robbery and menacing.
One of his victim's spoke to Eyewitness News about her horrible ordeal.
"All of a sudden, he came out of nowhere," Sylvia Serra said.
Right away, Serra said she knew something was wrong.
Wednesday morning, she got on an elevator at her building on Flushing Avenue in Williamsburg, but so did the suspect.
"He was fidgeting, he was kind of nervous," Serra said, "He had these pants, jean pants that had no zipper, he had buttons, and I noticed it was open, so that got me suspicious."
Police believe Williams approached another woman back on January 1 in another building nearby.
Except in that case, it was a 63-year-old woman who he allegedly forced off the elevator and sexually assaulted.
Sylvia told Eyewitness News that as she rode with the suspect in the elevator, he said he had a weapon, but she kept her cool.
"I think I was more composed, because I didn't want him to get more aggressive," Serra said.
That's when he forced her off the elevator on the 15th floor.
"I started running, I started banging on doors, I started screaming for my life, 'help, help, help,' and nobody came out and I was screaming, literally screaming for my life," Serra said.
It's true, say her neighbors.
They were too afraid to come out and help.
"I heard her screaming," neighbor Nellie Roman said.
"It's terrible, it's just horrible," neighbor Michelle Johnson said. "Women shouldn't have to fear their lives to come outside."
Sylvia, meanwhile, is relieved things weren't worse and says she's proud.
"I think I did pretty good, I think I did pretty good for what happened," Serra said.