Avonte Oquendo remains possibly found.

New York (CNN) -- A New York City woman whose teenage autistic son disappeared in October may be facing every mother's nightmare.

On Thursday night, police found legs and an arm next to the East River in Queens as well as size 5½ Air Jordan sneakers that match the shoes of her child, Avonte Oquendo, the teen's family attorney, David Perecman, told CNN on Friday.

Investigators also found size 16 dark jeans, the same size the teen wore, and underwear, the lawyer said.

Avonte's mother, Vanessa Fontaine, who has passionately advocated for a search for her son, will provide investigators with her DNA so they can determine whether the remains are the child's, the attorney said.

"She doesn't seem to me to have ever lost hope," Perecman told reporters Friday. "This morning when I spoke to her she just said, 'You know, it's not Avonte until it's Avonte.' "

Over months of searching for Avonte, his mother always held out hope. After he was missing for three weeks, she addressed reporters at an October 25 news conference.

"My thoughts are that my son is still out there, and I want everyone to continue to help me search for my son," Fontaine said. "He is not gone."

The idea of her son wandering around New York was terrifying because he cannot communicate verbally, she said soon after his disappearance.

"He has the mental capacity of a 7- or 8-year-old," she said.

Avonte was supposed to be with a monitor at all times, Fontaine said.

But surveillance footage that captured her son bounding out of Center Boulevard School on Long Island at 12:38 p.m on October 4 did not show him with a supervisor.