A former New York City police officer was convicted on Wednesday of attempted assault for punching a man 13 times after the man’s girlfriend called 911 seeking help with her distraught son.

The former officer, Christian Zapata, 37, was sentenced in the nonjury trial to time served, meaning he will not spend time behind bars. He was acquitted of a more serious charge, third-degree assault, which could have carried up to a year in jail.

Justice Curtis Farber said Manhattan prosecutors chose not to call the victim, Jerome Collins, as a witness and a review of medical records failed to show that he had suffered injuries.

“This was a single, abhorrent act by Mr. Zapata,” Judge Farber said during the sentencing hearing in Manhattan Supreme Court, according to court transcripts. “He otherwise led an unblemished career as a New York City police officer and police sergeant.”

Mr. Zapata, who resigned from the department on Jan. 3, was a sergeant on Dec. 7, 2022, when he and other officers responded to a Harlem apartment after a mother called for help because she was unable to calm her 15-year-old son, who is autistic.

When the officers came inside, Ms. Turner’s boyfriend, Mr. Collins, asked them to put on masks, according to court documents and video footage captured by the officers’ body cameras. The police officers refused and the exchange escalated into a confrontation that ended with Mr. Zapata grabbing Mr. Collins and punching him as another officer held down his hands. The punching only stopped after another officer came between the two men.

Mr. Collins was then placed in handcuffs and taken into the hallway as his 8-year-old son began weeping, according to the video footage.

“Daddy is all right,” Mr. Collins told the boy.

“Are you going to come back?” the boy asked.

“Yes, what did Daddy tell you? He always comes back,” Mr. Collins replied before officers dragged him away.

Mr. Zapata told the boy, who was still crying, “I’m sorry, young man. I’m sorry you had to see that.”

Mr. Collins, who at the time worked as a home health aide, spent 24 hours in detention and was charged with resisting arrest and obstruction of justice. Both charges were dismissed. He was treated for his injuries and did not need to be hospitalized.

Mr. Zapata retired before the department could discipline him, the police said. He was demoted to the rank of officer following the assault.

Prosecutors asked Judge Farber to sentence Mr. Zapata to 60 days in jail, saying he had “brutally assaulted Mr. Jerome Collins without justification.” Even after being suspended and demoted, he “has been unwilling to admit that what he did that day was wrong,” said Tavish DeAtley, an assistant district attorney.

Mr. DeAtley said that prosecutors had called as witnesses two officers who were with Mr. Zapata that day and said they “bravely testified about their supervisor’s egregious conduct.”

Mr. Zapata’s lawyer, Andrew Quinn, did not respond to messages for comment on Wednesday afternoon.

During the sentencing hearing, Mr. Quinn said Mr. Zapata had “momentarily lost control” and “threw more punches than was necessary.”

“He was doing his job to the best of his ability,” Mr. Quinn said. “The bottom line is, everybody went home safe, and the young man got the help he needed. I consider that a job well done.”

Mr. Zapata declined to speak before he was sentenced, but nodded along as his lawyer spoke, according to court transcripts. Mr. Quinn said that before that day, Mr. Zapata had made more than 400 arrests and never been the subject of a complaint from the public.

Judge Farber declined to impose the 60-day sentence, saying that Mr. Zapata “was already, tremendously, punished by losing his position as a sergeant, being demoted and ultimately forfeiting his job and career as a police officer, and benefits that flowed from there.”

Alvin L. Bragg, the Manhattan district attorney, said in a statement that “the use of unlawful force cannot be permitted.”

“Holding members of law enforcement accountable when they break the law is essential for public safety and upholding the public’s trust,” he said.