A single bullet fired by an armed teenager struck a police officer and the gunman as they scuffled during a confrontation in the Bronx late Tuesday, officials said. Both were expected to recover from their injuries. Mayor Eric Adams, speaking at a news conference at the hospital where the officer and the 16-year-old suspect were being treated, said the episode was an “unacceptable” example of the gun violence that is plaguing parts of New York City. Mr. Adams said the suspect, whose name was not released, had been sentenced to probation in December after being arrested with a gun in the Bronx last May. The mayor said the suspect, who police officials said had gang ties, had also been arrested with a gun at 14.“What is it going to take,” Mr. Adams said, “before we realize that we are endangering the lives of children by allowing children to carry guns that they are using on children.”Echoing the calls of many law enforcement officials, the mayor, a former police captain and transit officer, implored state legislators to do what they could to stem the tide of violence among young people.“We need help,” Mr. Adams said, speaking in somber tones. “We need our lawmakers to look at this.” Police officials gave the following account of the events that led to the shooting:At around 9:30 p.m., a group of six uniformed officers in two unmarked police cars were patrolling near Lorillard Place and East 187th Street in the Belmont section. The area is close to the Little Italy neighborhood known for the shops and restaurants that line Arthur Avenue. Noticing a loud group of about a half-dozen people gathered outside a building that the police consider a locus of drug and gang activity, the officers approached. As they did, the 16-year-old suspect shoved his hands in his pockets and moved toward a car parked nearby. The officers told the teenager to take his hands out of his pockets, and he refused. After he ignored several more orders to show his hands, one of the officers began to scuffle with him. In the skirmish, the gun went off once, with the bullet striking the teenager in his groin and then hitting the officer in the right leg below the knee.Keehant Sewell, the police commissioner, said at the news conference that she had reviewed footage captured by the officers’ body-worn cameras and that none had fired their weapons.James Essig, the Police Department’s chief of detectives, said that one bullet and a 9-millimeter Sig Sauer handgun that had been reported stolen in South Carolina in October 2020 were recovered at the scene. Mr. Adams praised the officers for using “proper police tactics” and for taking a gun off the street “without taking a life.” The officer who was shot on Tuesday was the second to be hit by gunfire in the city this month. Early New Year’s Day, an off-duty officer was hospitalized after being shot in the head while he slept in a car outside an East Harlem station house between shifts, officials said. The officer, who sustained a fractured skull in the episode, left the hospital the next day after undergoing surgery, cheered on by his colleagues.Mr. Adams pledged during his campaign to focus on improving public safety. He has continued to emphasize the issue and his commitment to fulfilling his vow since taking office on Jan. 1. In addition to his public appearances after two officers were shot, he has been front and center following several other violent incidents in the early days of his term, including a fire in the Bronx that killed 17 people, the deadly shooting of a 19-year-old Burger King employee in East Harlem and the fatal shoving of 40-year-old woman into the path of a subway train in Times Square last weekend. “Our city must be safe,” Mr. Adams said at the news conference. “That is the promise I made and that is the promise I am going to keep.”