President of the Detectives' Endowment Association Paul DiGiacomo provides insight into violent crime soaring in major U.S. cities. A person of interest was reportedly being questioned by New York City police on Saurday night in connection with a series of slashing attacks on the city's subway system. No charges were yet filed, reporter Yan Kaner wrote on Twitter. Earlier Saturday, the New York Police Department announced that 500 more police officers will be patrolling subway stations after the fatal stabbings of two homeless people plus two other victims in the previous 24 hours. "We will immediately commence a surge of officers to patrol both above and below grounds to ensure that everyone that rides on our transit system on a daily basis not only is safe, but just as importantly, feels safe," NYPD Commissioner Dermot Shea said in a news conference Saturday afternoon.