NEW YORK (AP) — Two 14-year-old boys pleaded not guilty Wednesday to murder in the death of a Barnard College student who was fatally stabbed during a robbery in a park.

Manhattan prosecutors said that Rashaun Weaver stabbed 18-year-old Tessa Majors during a Dec. 11 robbery and that Luchiano Lewis prevented her from escaping as she called for help.

A 13-year-old has also been charge, but his name has not been released because he is being tried as a juvenile. The Associated Press is identifying the 14-year-olds because of the seriousness of the crime and because they are charged as adults.

An attorney for Lewis said he had no comment on the charges. A phone message was left with an attorney for Weaver.

Weaver was arrested on Feb. 14 and Lewis was arrested Wednesday after a two-month investigation into the stabbing in Morningside Park near the Barnard campus in upper Manhattan.

“While a criminal process will never fully heal the unimaginable pain suffered by Tessa Majors’ family and friends, this indictment is a significant step forward on the path to justice,” District Attorney Cyrus Vance Jr. said. “We are committed to holding these young people accountable, and equally committed to a fair process which safeguards their rights. This is how we will achieve true justice for Tessa and her loved ones.”

Police Commissioner Dermot Shea said, “Detectives, investigators and prosecutors, as well as a grand jury, worked deliberately to ensure that the evidence amassed supported the charges brought, and that now those who allegedly murdered Tessa Majors will be held to account. Nothing can bring her back. That is the tragedy we all must live with.”

Majors, who played in a rock band and aspired to study journalism, was stabbed as she walked through the park in the early evening. She staggered up a flight of stairs to street level and collapsed. She was pronounced dead at a hospital.

Prosecutors say Majors fought back against her attackers and DNA from her fingernails matched Weaver’s DNA. They say Weaver was heard on an audio recording describing hitting Majors with a knife.

Weaver has also been charged with robbing another person in the park.