A teen-ager pleaded not guilty to firing the gunshots that killed a Fresno man during a four-hour Labor Day weekend shooting rampage. Jermaine Johnson was arraigned on a first-degree murder charge and 17 other charges Friday. He was identified as the gunman in the death of Victor Diaz, 49, who was shot in front of his home, said Deputy Dist. Atty. Gary Hoff. Nine others were wounded in the shootings. A juvenile court official ruled earlier this week that Johnson would be prosecuted as an adult. Another 16-year-old arrested with him faces a similar hearing in two weeks. Two others, ages 14 and 15, will be tried as juveniles. All four face one charge of first-degree murder in Diaz's death, as well as six counts each of attempted murder, five counts of armed robbery, and six other felony counts.