REVERE – A former Army sniper who wanted to become a police officer chased the person who shot and killed him last Saturday night, before collapsing on a Boston street, a friend said Monday.Revere native and Everett resident Stephen Perez, 22, was pronounced dead at Tufts Medical Center Saturday morning after Boston police officers responded to a shooting on a downtown section of Tremont Street, according to a Boston Police Department press release.Rob Marston, a Revere resident who identified himself on Monday as the husband of Perez’s cousin, Andrea, said he was told Perez and friends left a Boston club following a fight. They were sitting in a car outside the club when another vehicle pulled up alongside the car with individuals from the fight inside the vehicle.Marston said Perez and another individual were fighting when someone else got out of the vehicle and shot Perez in the back.”Steve chased him more than 100 yards, I was told, and then collapsed,” Marston said.According to the police release, the Boston Police Homicide Unit encourages anyone with information on the shooting to call 617-343-4470.Marston and his wife said Perez grew up in Revere with his father, a Roland Road resident, and younger brother, Salvatore. He graduated from Revere High School in 2007 and joined the Army in part to give himself a leg-up on finding a job once he got out of the service.He served two tours in the Army spanning four years and specialized as a sniper. Once he returned home, he enrolled in Bunker Hill Community College’s criminal justice program.”He aspired to be a policeman. He was just a good guy,” Marston said.Although he was living with friends in Everett, Rob and Andrea Marston said Perez visited his father several days a week.Thor Jourgensen can be reached at [email protected].