At 14, He Fired a Fatal Shot. At 18, He Was Finally Sentenced.

It was a killing that connected two very different young lives.

Timi Oyebola was 16 when he was shot to death while playing basketball at Chester Playground in the Brownsville neighborhood of Brooklyn on a September afternoon in 2018.

The boy who fired the fatal shot, Aaron Nathaniel Jr., was even younger — just 14.

The case prompted a public outpouring of grief because of the uncommonly young age of both the killer and the victim, but after Mr. Nathaniel’s arrest, the justice system seemed to grind to a halt. By the time he pleaded guilty to murder last month, Mr. Nathaniel was 18; he had spent more than 1,300 days at Crossroads Juvenile Center in Brownsville.

On Monday, three and a half years after Mr. Nathaniel’s arrest, Judge Craig S. Walker, who oversees the Youth Part of the Kings County Supreme Court in Brooklyn, sentenced Mr. Nathaniel to 10 years to life, calling it the harshest sentence he had imposed on a young person.

Mr. Nathaniel nodded as the judge sentenced him but did not speak during the brief hearing, shaking his head when the judge asked if he wanted to address the court.

The case represents an unusual example of the way New York adjudicates crimes involving so-called juvenile offenders — minors who face accusations so serious that they are treated much like adults. In New York, which has one of the youngest age exceptions in the country, children as young as 13 can be tried asjuvenile offenders for violent crimes.

The delays in the case — partly but not entirely related to the pandemic — also renewed concerns about New York’s spotty record on defendants’ right to a speedy trial, and left both childrens’ families discontented.

Timi’s father, David Oyebola, said in an interview on the night of his son’s murder that he had already forgiven the killer, and in another interview before the sentencing, said he prays for Mr. Nathaniel every day: “That his life takes a new turn, that God continues to visit him.”

But during the sentencing, he also expressed his frustration to the court during a video conference call from Indiana, where he and his family now live.

“Justice delayed is justice denied,” Mr. Oyebola said. “Your delay of this case from 2018 until now destroyed my faith in the system and showed how insensitive you are and how flawed your system of justice to be.”

Mr. Nathaniel will be held in a youth facility until he is 21, when he will go to an adult prison, a spokeswoman for the New York State Office of Children and Family Services said.

“This heartbreaking case highlights the devastation gun violence wreaks in our communities,” Eric Gonzalez, the Brooklyn district attorney, said in a statement. “A promising life has been cut short, a family remains in mourning, and after living through a troubled childhood, this young defendant’s future is now in ruins.”

The sentencing on Monday shed little new light on the circumstances of the killing. A witness told the police that Mr. Nathaniel had been angered by Facebook comments about the stabbing death of a friend, one of four teens killed in Brownsville that July. But Timi had nothing to do with the deaths and was not the intended target, according to the District Attorney’s Office.

“I understand the pain and there’s pain on both sides. There are no winners here at all,” Judge Walker said during the hearing. “The Oyebolas have lost a son that they can never see again, that they can never hold again, that they can never speak to again, and although Mr. Nathaniel is still here, he is also not going to be present in a sense in his family’s life.”

The two boys had come from very different backgrounds when their lives intersected violently that day in 2018.

Timi’s full name — Oluwadurotimi — means “God stands with me” in the Yoruba language of Nigeria, where he was bornand lived until he and his sister joined their father in New York in 2013; his mother followed three years later.

In New York, Timi worshiped twice a week at a church in Brownsville where his father was a pastor. Less than a week before Timi died, youth group leaders asked everyone to describe themselves with an adjective starting with their initial. Standing 5-foot-5, Timi dryly declared himself “Tall Timi.”

Sometimes, he sneaked out to play basketball, but he was so quick that those trying to catch him would only later find him back in the sanctuary, a Bible in his lap.

Growing up in Brownsville, Mr. Nathaniel was still a baby when his father started passing in and out of jail, ultimately serving time for armed robbery. By around 2007, Aaron Nathaniel Sr. told the family to stop making the 16-hour round trip bus ride to visit him in prison, and Mr. Nathaniel was 9 before he saw his namesake again.

A quiet kid, Mr. Nathaniel was happiest on the basketball court, his father said. He spent hours playing pickup games.

But a learning disability made school difficultand Mr. Nathaniel started getting into fights, so his father said he brought him to Connecticut, where he had eventually moved after his release. But by summer 2018, around the time of his friend’s stabbing, Mr. Nathaniel had shut down, and his father sent him back home to Brooklyn.

Mr. Nathaniel dropped out of school. Within months, he was arrested for Timi’s murder.

The case against Mr. Nathaniel was in the public eye from the beginning. Block-by-block video footage depicted him running from the playground, carrying a gun. For nearly two weeks, the police could not find him, so officers at Brooklyn’s 73rd precinct shared pictures and his name on Twitter.

Cases involving minors are typically secret, but murders in New York are handled differently. After Mr.Nathaniel’s arrest and confession, he was treated sometimes as a child, sometimes as an adult.

The murder case was held in open court and will remain on his adult record, his identity unprotected. But three assault charges he racked up behind bars are sealed because he was not yet 18.

As New York’s judicial machinery slowly ground on, Mr. Nathaniel was growing up behind bars.

The state guarantees a speedy trial — defined as six months for felony accusations — but murder cases are excepted from that law. Another state law that required prosecutors to submit evidence by strict deadlines was not on the books until the year after Timi’s killing.

For the first year and a half after his arrest, there was little progress on his case. Then, the pandemic closed courtrooms all over the country. In all, Mr. Nathaniel spent nearly the entire duration of what would have been his high school years awaiting trial.

“The notion of holding a child for an extended period of time, an extraordinary time in Aaron’s case, is unconscionable, especially without a finding of guilt,” said Kristin Henning, a law professor and director of the Juvenile Justice Clinic & Initiative at Georgetown Law.

Mr. Nathaniel appeared to languish during his incarceration.

His father said he visited him at Crossroads as often as once a week. Last year, he began noticing red gashes on his son’s arms: He was cutting himself, and was put on suicide watch.

Crossroads is just two blocks from Howard Houses, the Brownsville housing project where Mr.Nathaniel grew up. He can see the apartment building from a window, his father said.

“He’s literally looking at his life pass,” Mr. Nathaniel said. “I think that’s extreme torture.”

The passage of time between his arrest and sentencing was plain in the two court hearings.

At his arraignment in October 2018, Mr. Nathaniel was escorted into court in handcuffs, a blue T-shirt pulled over a sweater, bluejeans hanging low on his 5-foot-4 frame.He kept his head down, watching the prosecutor a few steps away, out of the side of his eyes. He turned once to look back at his mother, seated on a bench behind him.

At his sentencing on Monday, Mr. Nathaniel walked into court in a white collared shirt and bluejeans, hands cuffed behind him, a light blue mask covering his face. He towered over his lawyer, bowing his head to whisper to her throughout the about 20-minute hearing. Five dark scars ran across his right forearm.

He asked through a lawyer if he could meet with his mother, who along with his father, had come to support him with eight other friends and family.

“Right now we are really pressed for time,” Judge Walker said, denying the request.

Susan C. Beachy contributed research.