Jonaiki Martinez Estrella, 25, who delivered the fatal blow by stabbing Junior in the neck, was sentenced to life in prison without parole.
Prosecutors said that he was not remorseful and that, in fact, a correction officer found him in a one-inch sharp object in his shoe on the way to court Friday morning.
In court, he told the judge, "I'm sorry" and "My intention was not to cause death," blaming drugs, alcohol, and allegiance to the Trinitarios gang. His attorney says he plans to appeal.
Twenty-five-year-old Antonio Rodriguez Hernandez Santiago, 23-year-old Jose Muniz, and 25-year-old Elvin Garcia were all sentenced to 25 years to life, while 19-year-old Manuel Rivera was sentenced to 23 years to life because of his age at the time of the crime.
Junior's mother and father delivered heartbreaking victim impact statements, saying that justice was served but their lives will never be the same
It was a moment Leandra Feliz has been waiting to do for months, after the sentencing had been delayed three times.
"They killed an innocent child," she said. "Of all these men, not a single one of them said, 'No, no, don't do it.' That night, there were two deaths, Junior and I, who was left dead inside. As a young boy, my son dreamed of becoming a detective, so he could protect this city...Please make sure my son's dreams come true. These killers should never be able to step out of a jail cell, so they know the moment they killed my son, they took their own lives as well."
WATCH: Junior's family reacts to the sentencing
Lisandro Guzman, Junior's father, said he can't sleep and that weekends are the worst because that's when he would spend time with his son.
"I struggle daily to find meaning in my life," he said. "I am no longer the person I once was. It is impossible to find purpose in life. You will never have the ability to understand the pain that you caused. I will never forgive you. You deserve to be punished to the fullest extent of the law."
In June, a jury found the men guilty of first-degree murder, second-degree murder, conspiracy and second-degree gang assault, for the June 2018 murder of 15-year-old Junior.
Surveillance video from a Bathgate Avenue bodega showed some of them dragging Junior out into the street where he was stabbed to death, only about a block away from his apartment.
The brutality of the murder drew nationwide attention and sparked the #JusticeForJunior hashtag.
Since the murder, his mother has moved away. Her new home is filled with pictures and artwork paying tribute to her son who had planned to someday become a police officer.
Eight other defendants in the case are still awaiting trial.
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