One of three teenagers charged in the 2019 stabbing death of a New York City college student inside a park pleaded guilty Tuesday to all the charges against him.

The 16-year-old entered a guilty plea to second-degree murder and first and second-degree robbery in connection with the death of Tessa Majors, his lawyer, Alex Padilla, told Fox News. 

"We are aware of today's proceeding involving the second guilty plea," the Majors family said in a statement. "We remain resolute in our belief that all parties who bear responsibility for Tess's senseless death will be held accountable, and we are deeply grateful to the many people who continue to pursue that goal."

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The 15-year-old charged with fatally stabbing Barnard student Tessa Majors during a park mugging was caught on a wiretap confessing to his jailed dad, sources said.

"In particular, we would like to thank the members of the Manhattan District Attorney's Office and the New York City Police Department for their tireless and thorough efforts," the family added. "We have maintained confidence in their work from the beginning and appreciate their diligence and the compassion they have shown us."

Padilla declined to comment on the matter but disputed other reports that said his client was cooperating with prosecutors against his co-defendant, who is also 16. He denied that was the case. 

Fox News has reached out to the Manhattan District Attorney's Office, which declined to comment. 

Another suspect, who was 13 at the time of the stabbing, pleaded guilty last year to first-degree robbery and was sentenced to 18 months in detention. 

Outside the courtroom on Tuesday, the lawyer for the teen still facing charges, Jeffrey Lichtman, said: "This was not a premeditated murder as we heard inside. These were 14- and a 13-year-old boys, and we should remember that," WABC-TV reported. 

Prosecutors allege the three teens were looking for people to rob when they tried to mug Majors, an 18-year-old Barnard College freshman, in nearby Morningside Park on Dec. 11, 2019. 

People pause and place a candle at a makeshift memorial for Tessa Majors inside the Barnard campus. (AP)

The youngest suspect previously told a court he and two accomplices entered the park intending to commit a robbery. After opting against robbing the first person they came across, the teen told detectives his friend "dropped a knife" while putting Majors in a chokehold. The teen suspect picked up the knife and handed it back to his friend before making a slashing motion at his throat, and then saw his friend stab Majors. 

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The Charlottesville, Virginia, native was found dead near a staircase in the park with multiple stab wounds. She had staggered up a flight of stairs to the street level and collapsed.

The death left the community surrounding the all-women's college, which sits near Columbia University and Harlem, shaken and rekindled fears for many New Yorkers about the days when a nighttime walk through the park was considered dangerous. 

The 16-year-old suspect who pleaded guilty faces life in prison. He is due back in court on Oct. 18. 

The Associated Press contributed to this report.