BOSTON – A judge ordered a Salem man held without bail on a murder charge after police said the man fatally shot a 22-year-old Revere veteran in the back in 2012, Suffolk County District Attorney Daniel F. Conley announced Thursday.Peter Castillo, 26, pleaded not guilty in Suffolk Superior Court on Thursday to first-degree murder in the death of Stephen Perez Jr.Assistant District Attorney David Fredette told the court that Perez, a U.S. Army veteran who had served tours in Iraq and Afghanistan, was with friends in Boston’s Theater District in the early morning of April 28, 2012, when he got into a fight in a parking lot on Tremont Street. Castillo was not involved in the initial fight but received a phone call and – as members of the initial group confronted Perez – Castillo allegedly came up and shot Perez in the back.Castillo fled to the Dominican Republic shortly after the shooting and was captured in Santo Domingo on Jan. 15. Two Lynn residents are also charged in connection with the incident. Luis Sepulveda, 30, and Janice Hardy, 24, were indicted on charges of misleading an investigator and perjury after allegedly lying to police and the grand jury investigating the murder.Castillo is scheduled to return to court March 12. Sepulveda and Hardy are scheduled to return to court Feb. 26.