A 19-year-old man who was in mental distress and called 911 seeking help was fatally shot by the police in his Queens home on Wednesday after, officials said, he threatened officers with a pair of scissors and they opened fire.

But the man’s brother, who witnessed the shooting, contradicted aspects of the police account of events, saying his mother was restraining her son when he was shot and insisting that the officers had not needed to fire their guns.

The man, Win Rozario, was declared dead shortly after the shooting, which occurred around 1:45 p.m. in his family’s second-floor apartment on 103rd Street in Ozone Park, police officials said.

John Chell, the Police Department’s chief of patrol, said at a news conference that the shooting took place after two officers answering a 911 call about a person in mental distress went to the apartment, where the situation became “quite hectic, chaotic and dangerous right away.” The police believe Mr. Rozario placed the 911 call, Chief Chell said.

When the officers tried to take Mr. Rozario into custody, he pulled the scissors out of a drawer and “came toward” the officers, the chief said. Both officers fired their Tasers at Mr. Rozario and appeared to have him subdued, Chief Chell said.

“But a mother, being a mother, came to the aid of her son to help him, but in doing so she accidentally knocked the Tasers out of his body,” the chief said. At that point, Mr. Rozario picked up the scissors and came at the officers again, the chief said.

“They had no choice but to defend themselves, discharging their firearms,” Chief Chell said.

He did not say how many times Mr. Rozario had been shot. Mr. Rozario’s family said it was six times. The entire episode was captured by officers’ body-worn cameras, the chief said. The footage was not immediately released.

Mr. Rozario’s 17-year-old brother, Ushto Rozario, contradicted the police account in an interview. He said his mother had been holding his brother in her arms throughout the encounter.

“As my mother was still hugging him, they shot him with the Taser,” he said. “So they shot him with the Tasers, and my brother didn’t really go down. So one of the cops pulled out a gun and shot him as my mother still hugging him.”

He said the shooting was unnecessary.

“First of all, it was two police officers against him,” he said. “And my mother was already holding him, so he couldn’t really do anything.”

He added: “I don’t think a scissors is threatening to two police officers.”

Mr. Rozario was the third person in New York to be fatally shot by the police in the past two months. In February, officers shot a man in the Arverne section of the Rockaways who, officials said, pointed a BB gun at the officers who were responding to a 911 call of shots being fired. Last week, officers in Brooklyn fatally shot a man who, law enforcement officials said, had himself been firing at a mugger who was running away.

Francis Rozario, Ushto and Win’s father, said that the family had immigrated to New York from Bangladesh 10 years ago and that Win’s dream was to join the U.S. military. His plans had been held up, however, by a delay in the family’s obtaining their green cards, which the elder Mr. Rozario said had been approved last year.

Ushto Rozario said his brother, who graduated from John Adams High School in Ozone Park two years ago, had been depressed recently, and his father said Win had been hospitalized briefly last year with mental health problems.

Nelima Efroze, who, with her family, owns the house where the shooting occurred and lives in the first-floor apartment, said the Rozarios had moved in about four years ago and had been good tenants who were quiet and always paid their rent on time.

“I never had any problem with them,” Ms. Efroze said.

Kenneth Clark, a retired Fire Department shop worker who lives two doors away from where the shooting occurred, said he was in his car in front of a nearby church waiting for a parking space to become available when he saw a police squad car pull up around 1:30 p.m.

The officers went into the apartment building “and the next thing you knew you heard some loud arguing and then a shot, and then in a minute or two later you heard three or four more shots,” Mr. Clark, 70, said.

In an effort to reduce the potential for 911 calls involving mental health crises to escalate into violent encounters with the police, New York City started a pilot program in spring 2021 under which mental health professionals and emergency medical workers respond to a portion of such calls in a small number of police precincts.

Officials say the program has been effective, and it has been expanded to more precincts since then but is still not citywide. The 102nd Precinct, where Mr. Rozario was shot, is among the precincts where it is not in place.

Donovan Richards, the Queens borough president, said in a statement that Mr. Rozario’s death was “further proof that all levels of government” must move with urgency to “dramatically increase our investments in all-encompassing mental health services.”

Sean Piccoli contributed reporting. Susan C. Beachy contributed research.