Gerald Nelson is the police chief who supervises Brooklyn North, the area that includes Brownsville. With some pride, Nelson calls his command the most challenging in the city, in large part because of the crime in Brownsville, which he attributes overwhelmingly to boys and men between the ages of 15 and 25. He said the Police Department’s law-enforcement strategy was focused mostly on monitoring and disrupting the loosely affiliated groups of boys, or crews, as they call them, using social media, because the crews like to brag about their exploits on Facebook. Nelson distinguishes between boys he calls “young stallions,” who are at “that age” with hormones raging, toeing the line between right and wrong, and boys who at 14 or 15 have already been arrested several times for serious crimes. The department lets the young stallions roam, offering what access it can to outreach and mentoring programs. Nelson devotes much of his resources to the others. “If you didn’t see police contact, and you didn’t see stop-and-frisk, and you didn’t see them being collared, believe it or not, you are following the good kids,” Nelson said.

But being a good kid in Brownsville does not bring the same promise as being a good kid in other places. Nelson describes a neighborhood that is improving — crime is down 71 percent over the last two decades — and in that context, a kid like Shamir, who has not fallen into the system, is a symbol of progress. Still, he seemed adrift. Whenever I asked him what he wanted in the future, his answer was swift and certain: “To make it out of the hood. Get up out of here.” Yet he said he had no idea how to do that, even with his parents’ apartment outside the projects that he could call home.

Shamir’s older brother Sonnie, who is 33, made it out, and he was around Shamir’s age when he did. He eventually went to college and worked as a bank manager before establishing himself as a touring rap artist. Now he has an apartment in the suburbs.

Sonnie played in the same parks as Shamir, but in the ‘90s, when the drug trade in Brownsville was at its height. When he was 9 or 10, a man interrupted his skelly game and told him and his friends to run along. “He said it in a nice manner, like he was about to serve hot dogs and hamburgers or something,” Sonnie recalled. Instead, the man shot another man and walked off.

Sonnie has nostalgia for that time, even though there was more crime, because at least the violence was predictable; people were fighting over something — drug money — not fighting over nothing. To some extent, the drug dealers contained the collateral damage. They could still be heroes. They parked their cars on the street that runs along 284 Park in a display of their riches. It was the era of Mazda Millenias and Mitsubishi Diamantes. “You see people who have chains, cars or money or always come through with pretty girls, and you see the way everybody acts when this person comes around, and you’re like, ‘Oh, I want that,’ ” Sonnie said. “Because it’s a good feeling.”

He saved his allowance for months to buy a gold chain and gold fronts for his teeth. He used some of his money from a part-time job to buy marijuana that he sold at a profit to buy sneakers. But he also left the neighborhood every chance he got, for math and chess tournaments and basketball games, following the lead of his mother, who earned bachelor’s and master’s degrees while working office jobs. He was the overachiever among his friends. “I was pretty much into the whole school thing,” he said.

When he was 15, his best friend stole a safe belonging to his best friend’s uncle. “He was like, ‘We’re going to buy sneakers every week!’ ” The uncle threatened to kill his nephew and all of his friends, including Sonnie, so Sonnie’s best friend killed the uncle. “For my mom, that was the last straw,” he said. She sent him to Virginia to live with his grandmother.