An NYPD sergeant shot and killed an armed man during a prostitution sting in Brooklyn-Queens Expressway Thursday night, police said. Tyjuan Hill, 22, and three other men were in a green Mazda sedan when cops, suspicious that they were trying to solicit an undercover police officer posing as a prostiute, pulled their car over at Henry and Huntington streets about 10 p.m., sources said. That's when Hill bolted from the car and the sergeant and at least one other cop part of an operation dubbed Operation Losing Proposition gave chase, the spokesman said. When they caught up to Hill at West 9th Street and Hamilton Avenue, a struggle ensued. At some point, police said Hill drew a .9mm Kel Tec semiautomatic handgun and pointed it at the officers, police said. The sergeant an eight-year veteran who had never previously fired his gun squeezed off a round, striking Hill in the head, the NYPD spokesman said. Hill was pronounced dead at the scene, cops said. A gun was recovered at the scene. Police did not identify the sergeant who fired his weapon. Carol Hill, Tyjuan's mother, rejected the NYPD's version of events, saying her son never carried a gun. "He knows better than to carry any type of weapon," Hill, 44, said Friday. "I'm telling you, the police are lying." Carol Hill said she last spoke to her son at 9:30 p.m. Thursday, when he told her he was on his way home. When he failed to show up, she called his cell phone all night. "I felt something in my stomach, because my son wasn't home," she said. "I got scared, I got nervous." An NYPD detective notified her about the shooting the next morning, but she was too distraught to hear most of the details. "I was too busy screaming," she said. Cops were still questioning the other men in the car who are between the ages of 18 and 25 years old Friday afternoon, police said. They have not been arrested. One of the officers was taken to a hospital with minor injuries, police said. An NYPD spokesman said Hill had prior arrests for robbery, assault and narcotics. He had spent a year and a half in prison for robbery, according to state Department of Correction records and Hill's mother. Carol Hill said her son had "normal teenage problems," but would never threaten a police officer. "He stayed away from trouble," she said.