MORNINGSIDE HEIGHTS, Manhattan (WABC) -- A 13-year-old boy is now under arrest in connection with the stabbing death of Barnard College freshman Tessa Majors.
The NYPD reportedly picked up the teen Thursday afternoon in an apartment building on West 119th Street. They were holding him for criminal trespass when they say he began to discuss the girl's murder, and sources say he made statements implicating himself.
He was in possession of a knife, though police say it is unclear if that was the murder weapon. He will be charged as a minor with murder, robbery, and weapons possession, but as he is a juvenile, the case is being handled in family court.
That means the charging documents are unlikely to be made public, and his identity is likely to be kept a secret. He appeared before a judge Friday, and the arresting officer testified the juvenile was not the actual killer but picked up the knife and gave it to one of the other teens.
The 13-year-old attends MS 180 on West 120th Street, and detectives believe two other teens suspected of being involved in the crime likely do as well.
Sources familiar with the case say the 13-year-old also implicated the others, one of whom is a 14-year-old boy who police have located and who is being interviewed. A second teen has not been located.
Authorities say the statements from the 13-year-old match what detectives saw on surveilance video. The suspects are believed to have gotten away with the victim's bag, but they dropped her cell phone, which is how police identified her.
Commissioner Dermot Shea tweeted that the NYPD is "making significant progress, and we will have major updates to announce very soon."
The 13-year-old has been accompanied by his aunt during the NYPD investigation. She maintains her nephew's innocence. The boy's mother is no longer alive.
"I am absolutely confident that any individuals involved in this terrible heinous attack will be brought to justice and will be brought to justice quickly," Mayor Bill de Blasio said.
Majors, of Charlottesville, Virginia, was wrapping up her first semester at the school when she cut through Morningside Park just before 8 p.m. Wednesday. As she approached the stairs to exit at West 116th Street, police say a group of teens tried to rob her and take her phone.
There was a struggle, and she was stabbed multiple times. She stumbled to a guard booth to get to help. The university says a guard was on duty and was able to provide some assistance.
Majors was rushed to St. Luke's Hospital and pronounced dead.
"We are devastated by the senseless loss of our beautiful and talented Tess," her family said in a statement. "We are thankful for the incredible outpouring of love and support we have received from across the country. We would also like to express our appreciation for the efforts of the men and women of the NYPD, who continue to work diligently on this case."
The college, the wider Columbia University community, and New York City as a whole are in mourning, and memorials with flowers and candles now stand near where she was found and on the Barnard campus.
Students at Barnard College expressed their grief and wondered how it could have happened.
"It's very heartbreaking, that's it," one student said.. "Like genuinely, my thoughts and prayers go out to her family."
Reward posters have gone up around campus, and NYPD dive teams spent much of Thursday searching Morningside Pond for evidence.
"It's really shaken up the community," student Katie Long said.
Other students were calling more security.
"There should be 24/7 security guards," student Marwa Khairy said. "Personally, when I go through the park, I almost never see a security guard."
Investigators were still combing the park for evidence on Friday.
A police helicopter was overhead as dive teams searched Morningside Pond to see if the suspects discarded anything there.