Domingo Tapia and Gary Anderson crossed paths for no more than a second, two lives colliding in a moment of grainy surveillance footage.

Mr. Tapia, a 38-year-old Mexican immigrant who worked as a fruit vendor, had met his brother for a few beers on a summer evening in 2017. They had passed the time and said their goodbyes.

He turned back momentarily to retrieve a bag of fruit he had forgotten at the bar, mounted his bike and glided off toward his wife and two sons, through the quiet streets of Bedford-Stuyvesant, Brooklyn. It was 1:30 a.m.

Two blocks away, Mr. Anderson, a 26-year-old fitness trainer, was standing at Fulton Street and Albany Avenue among a group of men milling around the corner, gesticulating, apparently arguing.

Suddenly, he stalked into the crosswalk, advancing at just the moment Mr. Tapia pedaled into his path. Mr. Anderson took a step, and another, and then he exploded, launching his fist into Mr. Tapia’s face.

Mr. Tapia’s balance failed. The bike spun out. His head smashed against the hard, dark pavement.

The two men didn’t know each other, and they never would. The punch had arrived like many crimes in New York — random, swift, a bolt out of nowhere.

Mr. Tapia was rushed to the hospital and placed in a medically induced coma, where he remained, motionless in a white room, a tangle of tubes jutting from his chest.

Mr. Anderson was arrested and indicted on several charges, including felony assault. For almost three years, he bounced among prisons in upstate New York, while Mr. Tapia’s wife, Esther Diaz, sat day after day at her husband’s bedside, praying for his limp body to stir.

Outside, seasons changed, his sons grew into teenagers, the city churned on. Nearly seven years slipped by, measured out by beeping monitors.

Last March, the monitors went silent.

A Typical Morning

Ms. Diaz and Mr. Tapia both immigrated from Guerrero, Mexico, but they met more than 2,000 miles from home at a restaurant in Flatbush.

Ms. Diaz had been waiting on tables amid a crush of customers when Mr. Tapia walked in. They talked through the busy afternoon, the restaurant abuzz around them. A bouquet of roses arrived the following week. They found home in each other: Ms. Diaz bright and energetic at just over 5 feet tall, and Mr. Tapia her calm and gentle counterpart.

Over the next 15 years, they built a life together in Brooklyn and welcomed a son, Pedro, and then another, José.

Mr. Tapia was an attentive father, Ms. Diaz said. He rarely stayed out late, preferring to come straight home from work to spend time with their sons. The couple never married, partly because of concerns over their immigration status — both were undocumented — but they considered themselves husband and wife. They had a gentle war over the television: She liked telenovelas, he liked video games.

On the morning of June 7, 2017, the couple got up in a hurry and rushed to ready the children for school. Ms. Diaz bathed the boys, 5 and 7, in the kitchen while Mr. Tapia showered. The apartment was a blur of activity as the children collected their bags and Mr. Tapia rushed out. The door clicked shut before she had a chance to say goodbye.

By evening, Ms. Diaz could sense that something was amiss. Mr. Tapia had not answered a text message since he left. Eight p.m. and then 9 p.m. came and went without a word, the fresh tortillas and mole she had prepared growing cold on the table.

She awoke hours later to her buzzing phone. It was Kings County Hospital.

Seven Years of Waiting

When Ms. Diaz arrived, her husband was lying in a bed, bruises blooming across the back of his dented skull. Nurses hurried around the room, preparing him for surgery. Again and again, Ms. Diaz asked Mr. Tapia who had done this to him, but he couldn’t move his mouth. Instead, he took her arm and shook it.

He emerged from surgery hours later in a medically induced coma.

For nearly a week, Ms. Diaz had no idea what had happened. Detectives at the hospital offered little help. Calls to the police turned up few answers. At one point, the hospital staff even barred Ms. Diaz from entering her husband’s room until she could produce documents proving their relationship, which took days to procure from Mr. Tapia’s family in Mexico.

Frantic, Ms. Diaz contacted Hispanic news outlets, batting away the nagging fear that publicizing her name could threaten her residency.

Not long after, the police called her into the precinct. There, seated at a table beside her brother-in-law, she watched, numb, as officers played a fuzzy surveillance video. There it was: her husband, a stranger and a single punch rendered in choppy pixels.

Within days, the story of the inexplicable assault was splashed across tabloid headlines, unnerving the neighborhood and seizing New Yorkers’ attention for its particular brutality. At a candlelight vigil, Eric Adams, the Brooklyn borough president and future mayor, offered to personally pay $1,000 to anyone who could help.

Mr. Anderson was arrested at the end of that month. He had been building his personal training roster, hopping from gym to gym, when someone recognized him.

His arrest did little to calm Ms. Diaz. For weeks, the surveillance video of the punch played on every television, dragging her back to that night. On some days, she caught glimpses of Mr. Anderson roaming the neighborhood, out on bail. She would board a train car and he would be there. She would walk down the street and there he was.

In the evenings, after finishing work as a housekeeper, Ms. Diaz would trek to the hospital, traveling on foot when she couldn’t afford a MetroCard. She fed her sons dollar pizza for dinner before coaxing them to sleep at their father’s bedside in the intensive care unit.

There were unending bus rides and stacks of medical bills. The children’s grades plummeted. Pedro, the eldest, was being steadily bullied at school. Once, he got into a fight, telling her afterward that he had been defending himself so that he wouldn’t end up like his father.

Her sons deserved better, she thought. She was giving them a miserable life.

Mr. Tapia showed little improvement. He remained on a ventilator for six months, coming off life support for only two days before his body weakened again. A neighborhood activist and friend suggested that Ms. Diaz pull the plug, but she refused. She would pray for his recovery instead.

Years went by like that, and eventually Mr. Tapia was transferred to a long-term care facility in Staten Island. He sank into a vegetative state. Ms. Diaz did her best to travel to his bedside, but time and money were in short supply and the Verrazzano-Narrows Bridge loomed between them, a barrier dividing the family from its father.

The pandemic came. Visits dwindled.

An Unexplained Outburst

While Mr. Tapia’s family waited for him to wake, Mr. Anderson’s struggled to understand the burst of violence from a man they had known as a generous friend and doting parent.

Mr. Anderson was raised in Bed-Stuy, the youngest in his family. His half sister Shakeya Lloyd, who shares a father with him, said he had faced difficult circumstances growing up. He turned to fitness as a respite from troubles at home.

“Nobody knew of him as a troublemaker,” Ms. Lloyd said. “I’ve never even heard him raise his voice.”

She described her brother as charitable and thoughtful from an early age, bringing bags of Christmas gifts to his grandmother’s house and organizing donation drives in the neighborhood. Mr. Anderson always had girlfriends, she said, and over the years he raised three daughters. His Instagram account is dotted with photos of the girls, wobbling on roller skates and learning to read.

By June 2017, Mr. Anderson was working as a youth coach at the local Y.M.C.A. and running his personal training business on the side. He had never been arrested. So it came as a shock when Ms. Lloyd learned that her brother had attacked a man at Fulton and Albany.

In the months that followed, lawyers, politicians and even relatives had various theories about why he had swung. Prosecutors said he had been arguing with people on the corner. Later, they added that Mr. Anderson had decided to attack someone at random. One friend called it a bad moment; most were fuzzy on the details. Ms. Lloyd said she had been disappointed.

In September 2019, Mr. Anderson pleaded guilty to felony assault and was sentenced to three years in prison as Ms. Diaz looked on from the courtroom gallery. It didn’t feel like a punishment, Ms. Diaz thought. Nothing could soothe her family’s suffering.

‘Everything Is Coming Back Again’

Mr. Anderson did time at prisons in Ulster County and Altona in upstate New York. The five-hour trip was too long for his family to make regular visits and, though he called when he could, he struggled to explain his absence to his daughters.

In 2022, he was quietly released from prison, returning to Brooklyn. Yet again, Ms. Diaz encountered him on the street. She felt as though his eyes were on her back.

Mr. Anderson worked to rehabilitate himself, his family said. He opened a gym of his own and enmeshed himself again in his daughters’ lives. But court records tell of troubles fueled by alcohol and rage.

A few months after returning home, Mr. Anderson was arrested on charges of drunken driving and sentenced to a year of alcohol treatment.

Then in June 2024, he was charged with attempted murder, accused of shooting a gun at a man with whom he had argued at a bar. Mr. Anderson was released on bond. He attended every court date, standing behind a defense table once again.

Miles away in Staten Island, Mr. Tapia was fading away. In the months before, he had undergone two emergency surgeries, but before long his organs began to fail. On March 12, 2024, his body gave out entirely and he slipped away.

His hospital room was empty. Ms. Diaz couldn’t bring herself to go.

It was nearly a year later and Mr. Anderson had just finished his latest virtual appearance in his attempted murder case when his phone screen lit up with a call from his lawyer.

The medical examiner had ruled Mr. Tapia’s death a homicide, the case had gone to a grand jury and Mr. Anderson, his lawyer told him, had been newly indicted on manslaughter charges.

The news washed over him all at once, said Ms. Lloyd, Mr. Anderson’s sister. He had already admitted to punching Mr. Tapia and served time in prison. But when Mr. Tapia died, that changed the nature of the crime. Under the law, the attack was now not just a punch, but a punch that had killed a man.

Mr. Anderson surrendered on the new charges on Feb. 5. Detectives picked him up at the courthouse and brought him to a precinct and then back to court again. He stood in still another courtroom, listening as prosecutors once again described that night in June 2017, the endless moment his family and Ms. Diaz’s could not escape.

“It’s kind of wrong,” Ms. Lloyd said. Her brother had admitted his guilt and was remorseful. “How can it kind of slap you in the face?”

His lawyer, Judith Karpatkin of the Legal Aid Society, said she could not discuss the case.

Since his rearrest, Mr. Anderson, who was released on his own recognizance, has been active on Instagram, posting cryptically about the future. Last month, a neighbor in the building said he had cleared out his gym. Now it’s just a bare room under the J train tracks in Bushwick.

“I can take all the blessings I can get. I’m going through a lot,” Mr. Anderson said during a recent live video about repentance during Ramadan, which he observes.

“The past and bringing that back is very depressing,” Mr. Anderson said in the video, responding directly to a reporter’s request to talk about the case. “I felt like I did what I had to do, and now everything is coming back again.”

He declined to speak further.

Untouched Ashes

After Mr. Tapia’s death, Ms. Diaz had his body cremated. She brought his ashes home in a smooth wooden box and placed them high on a shelf at the back of a second-floor closet, where they remained, untouched, for the past year.

“Sometimes I didn’t understand how it was possible for us to survive all of these years,” Ms. Diaz said recently at her home in East Flatbush, fingering a sun-bleached photo of her husband, one of the few she has left of him.

Next month, when she returns to court for Mr. Anderson’s case, she’s hoping for just one thing. She wants to see her husband’s killer back behind bars.

“May he feel that pain,” Ms. Diaz said.

Seven years have passed since Mr. Anderson and Mr. Tapia met on the darkened corner of Fulton and Albany. But their two families remain frozen in that deadly moment.

Mr. Anderson, now 34, is facing the possibility of returning to prison. His daughters, the eldest of whom is almost a teenager, grapple with the prospect of losing their father again.

Ms. Diaz, 41, is raising her children on her own, the box with her husband’s ashes gathering dust upstairs.

From time to time, she can hear her sons, now 14 and 13, from behind a closed door, huddled over a glowing phone screen. They watch and rewatch the grainy clip of the punch that ended their father’s life.

Kirsten Noyes contributed research.