Gunmen assassinated a Salvadoran military court judge who presided over an investigation into the 1985 rebel attack on a San Salvador sidewalk cafe that killed 13 people, including six Americans. Alberto Serrano, 45, was gunned down about 7 a.m. in front of his home in El Salvador’s capital city, family members and police said. No one immediately claimed responsibility. Serrano had ruled that defendants in the 1985 case were covered by a law providing amnesty for political prisoners under the Central American peace plan. The judge also was in charge of investigations into a political case involving high-ranking military officers in a kidnaping-for-profit ring.