Police were called to the 137th Street-City College station at about 3 p.m., and when officers arrived, they found the teenager on the northbound platform of the No. 1 line with a stab wound to his abdomen. He was taken to Mount Sinai Morningside Hospital, where he was pronounced dead, police said. Police officials did not identify the victim and said no one had been charged. Police said they believed the boy and his attacker knew each other, although they did not know a motive. These incidents have subway riders concerned for their safety at a difficult time for the transit system. The attacks also presented a major political problem for Mayor Eric Adams, who pledged during his campaign to make the city safer. In surveys, commuters and employers said subway safety is a top concern. About 74 percent of commuters said they feel less safe using public transit now than they did before the pandemic, according to a March survey by the Partnership for New York City, an influential business group. In addition to these concerns, many riders still fear the spread of the coronavirus. About 79 percent of subway passengers who hadn’t returned to trains said social distancing was one of the biggest factors keeping them away, according to a customer survey conducted in the fall. The Metropolitan Transportation Authority, facing a potential crisis after massive revenue losses during the pandemic, desperately needs riders to return to its system. An infusion of state and federal money during the pandemic helped the agency stave off a deficit expected to reach $2 billion in 2026.