A man accused of gunning down a 17-year-old Moreno Valley boy and wounding his friend was charged Tuesday with first-degree murder and other offenses. Manuel Gomez, 52, of Moreno Valley, was arrested last week following a Riverside County Sheriff’s Department investigation. Along with murder, Gomez was charged with attempted murder and sentence-enhancing gun and great bodily injury allegations. The defendant pleaded not guilty during an arraignm…