The aunt of a 13-year-old boy charged in the murder of Barnard College student Tessa Majors denies that he’s responsible.

“We don’t know what’s going on,” the aunt said in an interview with The New York Daily News. “I’m sorry for that young woman, I am sorry for her family. But I know my nephew did not do this.”

The boy was reportedly arrested for second-degree murder, robbery, and a weapons charge. Police say up to three individuals robbed Majors at Morningside Park in Manhattan Wednesday evening. One of them stabbed the victim, officers said. Majors was pronounced dead at Mount Sinai St. Luke’s Hospital.

The boy did not confess to the murder, but did implicate himself, according to an official speaking with The New York Times.

“He didn’t do this,” said the teen’s aunt through sobs, according to the Daily News. “My nephew did not do that.”

Police said they are looking for other suspects allegedly involved in the case.

“This is an unthinkable tragedy that has shaken us to our core,” Barnard President Sian Beilock said in an email to the campus community Thursday, according to The Columbia Spectator. “Please know that we are all grieving together and I am thinking of you as we process this awful news as a community.”

[Image via Jeenah Moon/Getty Images]