At 860 Grand Concourse, a residential apartment building in the Bronx, the doorman’s post is just inside the front door, on a landing between two flights of stairs. One of them leads up to the offices of a dentist and a lawyer, who, along with several physicians, rent commercial space. The other leads past two pairs of gold-painted columns into the main lobby, where an elevator services seven floors with a hundred and eleven apartments. Tuesday through Saturday, between eight in the morning and five in the evening, tenants coming up or down from the lobby could expect a greeting from a trim, punctilious man with close-cropped hair. He wore a navy-blue uniform that hung loosely off his narrow shoulders. His name was Juan Sanabria.

There was an art to Sanabria’s salutations. Dana Frishkorn, who’s lived in the building for three and a half years, appreciated that he called her by her first name when she entered, and never failed to tell her “Take care” when she left. Yet somehow Sanabria knew that Anthony Tucker, who has spent five years in the building, preferred to be called by his last name. “Hey, Tuck,” Sanabria would say, extending his hand for a fist bump. When Tony Chen, who runs a boutique tour company and lives on the seventh floor, limped into the building one morning, addled by plantar fasciitis, Sanabria showed him a foot stretch that helped. On another afternoon, when a tenant showed up at the front door with a large couch to take up to his apartment, even though the building’s rules mandated the use of a side door, Sanabria stood watch to make sure a meddlesome neighbor didn’t wander over.

“With Juan, you always got the sense that he was more knowledgeable than he let on,” Georgeen Comerford, who has lived in the building for nearly fifty years, told me. A photography professor at CUNY, she described Sanabria as a “mensch who appreciated the ironies.” He would call her mámi, and wink, when she passed through the lobby. It wasn’t just that you were glad to see him, she said. “If you didn’t see him, you wanted to know where he was. When he wasn’t around, you felt it.”

Uncharacteristically, Sanabria wasn’t around the last week of February. His eighty-two-year-old mother, with whom he shared an apartment on Ogden Avenue, was suffering from emphysema; he’d been taking her to a nearby hospital. When word got around the building that Sanabria’s mother was ill, no one was surprised to learn that he was by her side. “It was who he was,” Jimmy Montalvo, one of the other doormen, told me. Montalvo and Sanabria were neighbors—Montalvo got his job at the building through Sanabria, three years ago—and frequently had breakfast together at their corner bodega; Sanabria was always bringing food back for his mother, Montalvo said. “He took good care of her.” Even when Sanabria was away from 860 Grand Concourse, during a break or on his days off, he gave the impression that he was never far. James Tirado, the youngest and newest doorman on staff, used to get calls and texts from Sanabria, checking up on him. “How’s the day going?” Sanabria would ask. “Is everything going O.K. for you?”

By the time his mother’s health had improved, and Sanabria returned to work, on March 3rd, he was beginning to feel ill himself. There were still very few publicly known COVID-19 cases in New York City, and his symptoms—dizziness and fatigue—were not yet widely associated with the disease. He wasn’t coughing, and he didn’t have a fever. He went home anyway, to rest for a few days. On Monday, March 9th, his day off, he returned to 860 Grand Concourse, to consult with a doctor on the first floor—his “doctor friend,” he called him. He was feeling worse, and had developed a cough. Tirado noticed him wheezing as he passed the doorman’s post.

While he waited for the doctor, Sanabria called one of his stepdaughters, Walkiris Cruz-Perez, a nurse at Columbia-Presbyterian. She was in the Dominican Republic at the time, getting dental work done, but she was concerned enough to call him an ambulance. “He would never call one for himself,” she said. “But I made him promise me one thing. I said to him, ‘Go to Columbia. Go to my hospital. Don’t go to Lincoln.’ ” She was referring to the Bronx hospital where Sanabria was born, and which he held in almost superstitiously high esteem. Lincoln was where he took his mother a week earlier, and where one of his best friends had died a few years before. He’d even considered applying for a part-time job there as a security guard.

It took about twenty minutes for the ambulance to arrive and for the orderlies to load him into the back. Not yet feverish, he insisted—in his usual, stoic way—that he was feeling just fine. What was most telling, though, was the fact that he did not object to being taken to the hospital; almost compulsively protective of others, he was finally ceding control to someone else, which struck Walkiris as worrisome. She talked him through the situation on FaceTime, as Tirado watched from the door. It would be the last time anyone from the building saw Sanabria.

In the days after Sanabria’s death, his former tenants and co-workers staggered between shock and grief. Contributing to the over-all sense of loss was their collective realization that, while they each felt extremely close to him, they actually knew little about him. Montalvo, for instance, was vaguely aware that Sanabria had served in the military, yet he never learned any of the details. One tenant in the building, a thirty-eight-year-old nurse and Navy reservist named Frankie Hamilton, knew about Sanabria’s time in the Navy because they swapped stories about training at a facility near Throgs Neck, in the Bronx. But he didn’t know anything about Sanabria’s family. At one point, another tenant told me, “I kept hearing that he had a daughter who was a nurse, but also that his daughter was a cop. Which was it?”

He had two stepdaughters, actually—a nurse and an N.Y.P.D. officer. He spoke about each of them constantly, with an unabashed and even grandiloquent sense of pride. Yet he shared stories about them in different ways to different people. Julia Donahue-Wait, a registered nurse herself, knew all about Walkiris’s career. But she would be at work during the day, when Sanabria’s other stepdaughter, Waleska, often dropped in to meet him for lunch. Waleska’s precinct, the Forty-fourth, includes the stretch of Grand Concourse where Sanabria worked. Several times a week, they went to a deli down the street and ate in his break room at the building. “When I didn’t have time, we would stand at the front door and talk about my son,” Waleska told me. Their conversations revolved around one of three things, she said: her child, her mother, or her work. “He loved that I was a cop. He was always telling me about things that would happen around the neighborhood.”

Sanabria, the son of Puerto Rican parents, grew up near the old Yankee Stadium, in the Bronx. After high school, he joined the Navy, where he served for the next twenty years. Travelling was an obsession of his—in the service, he spent time in the Philippines and the Bahamas—but he also loved structure and a sense of routine. “I used to say to him, ‘Juan, you’re just weird!’ ” Mimi Roman, his oldest friend, told me. (The two of them were born on the same day: August 13, 1967.) “He had to have everything in order. He’d always have his way of doing things.” After he was diagnosed with celiac disease, a digestive disorder that rendered him allergic to gluten, he adjusted his diet and stuck to it. “It was always everything in moderation,” Roman said.