King's friend discovered him shortly after 8 p.m. near Longbow Drive and Yorkshire Court in the Hunt Club condo complex, police said. Passersby and King's parents, called by the friend's mother, performed CPR until emergency responders arrived. He was taken to Kennedy University Hospital-Washington Township, where he was pronounced dead.
The Kings do not know how their youngest son died, and are hoping tests of tissue samples will provide insight. Police do not suspect a crime.
"He didn't have any medical issues [we know of]," King's father, Stanley, said. "That's what makes this extremely baffling."
King's coach, Larry Meglino, informed players' parents of the news Friday night and wanted to postpone the Minutemen Red's first game, against the Williamstown Braves. The players had another idea: They wanted to compete in his honor.
So the teammates wrote his number, 16, on their faces and donned black wristbands in a showing of solidarity.
"Instead of sitting home, letting that weigh on them, it kind of was therapeutic for them to go out and play," Meglino said. King's siblings and friends stood on third base at the game Saturday for a moment of silence.
The team eked out a victory, 10-9. The next day, it played again, winning by 12-2.
King had a way about him, Meglino said. He was the first to arrive at a volunteer field cleanup Thursday, and he'd often be the first player to start running to warm up. He was a third baseman and outfielder.
"In our dugout, if things got really serious in the game, he would say something out of the blue and make everybody laugh," he said.
It was a simple reminder, he said, of a sometimes-overlooked fact: "They are here to have fun. They are kids."
Thompson, a friend of the Kings, said: "He was really figuring it out, you know, really hitting the ball really good."
King was one of seven siblings. His parents, local lawyers, said their son grew up following baseball closely, rooting for the Phillies.
Off the field, King's hobbies were common among those his age: He enjoyed reading, playing video games, and watching sports (for football, he followed the Giants). He loved swimming and snorkeling.
On Monday, the school community wore red, King's favorite color, and a team of teachers crafted more than 600 red ribbon pins for students and staff, said Jim Barnes, principal at Chestnut Ridge Middle School.
Barnes said additional counselors were available to speak with students. Classmates created a banner with signatures, memories, and photos for the King family.
"He lit up a room," Barnes said. "A classroom, cafeteria, the bus. People gravitated toward him."
King was a "conscientious" student, said his social studies teacher, Marie Proko. The class was learning about life in the early 1800s and the War of 1812.
"We just did our high school course selections," Proko said. "We've been doing a lot of talking about their future. It's just so sad that he has been taken away at such a young age."
When students arrived at school after the weekend, Proko said, "usually people are laughing, joking - the hallways are noisy." This time, she said, "It was just silent."
A viewing is set to be Wednesday night, followed by services Thursday at the First Baptist Church of Jericho in Deptford.
In the days since his death, the boy's friends have filled social media with posts in his honor.
One friend reflected on Twitter: "Nadiir's impact is something no one can take away, long live the king."
"We had no idea he had the kind of impact he had on people," his mother, Sharon King, said.
King's memory will be honored on the baseball field this season, Meglino said.
The traveling league has ordered patches with his initials for the township's 200 players to wear above their hearts. And the Minutemen Red players will wear jerseys with King's last name and number during Sunday home games. But the loss does not go away.
"Every time we go out there and he's not there," Meglino said, "it's going to be another hard day."