Transcript for Developments in the tragic stabbing of a college student
breaking developments in the tragic fatal stabbing of an 18-year-old Barnard college student. Tessa majors made national headlines in December when she was attacked by a group of teenagers walking through a park in New York City. That crime sending shockwaves across the country. Tonight, a new arrest in the case. A 14-year-old charged with murder and other offenses. He will be tried as an adult. The Manhattan D.A. Says the evidence paints a gruesome picture and that Tessa majors' last words were, "Help me, I'm being robbed." ABC's Stephanie Ramos starts us off tonight. Reporter: Tonight, police arresting the teen they say is responsible for the brutal murder of Barnard college student, Tessa majors. The NYPD announcing 14-year-old rashaun weaver is being charged as an adult in her fatal stabbing. We are confident that we have the person in custody who stabbed her. Reporter: Authorities say blood evidence, smartphone evidence and the defendant's own statements paint a gruesome picture. Police describing her harrowing final moments. Some of the last words she was known to have said was, "Help me, I'm being robbed." Reporter: According to the criminal complaint, video surveillance shows majors entering morningside park just before 7:00 that evening. Weaver and two other teens allegedly enter around the same time from a different location, eventually confronting majors. Police say majors tried to fight back, leaving one of her attackers with bite marks. It was a painstaking, deliberate and meticulous search for the truth. Reporter: Weaver was wanted for questioning in the weeks after the killing, but ran away as he was being taken in for questioning. Eventually, he submitted to a police interview and DNA testing. Weaver is facing two counts of murder in the second degree. A 13-year-old alleged accomplice, who has been in custody for two months, faces a felony murder charge. The case gripping that New York City neighborhood with fear. Tonight, the district attorney vowing to honor Tessa, an 18-year-old freshman aspiring journalist and musician, with true justice. Stephanie joins us now from the neighborhood where the murder took place. And Stephanie, if found guilty, how much time could weaver face? Reporter: Well, Tom, weaver has still -- still needs to file a plea, but if convicted, he faces 25 years to life in prison. Police say he was arrested while at home with his family last night and he did not resist arrest. Tom? Stephanie Ramos with that update tonight for us. Stephanie, thank you.
This transcript has been automatically generated and may not be 100% accurate.