Sen. Dianne Feinstein, California Democrat and a longtime gun control advocate, denounced “the litany of massacres” over the past few years and asked rhetorically, “When will enough be enough?”

Mrs. Feinstein, who was first thrust into the national spotlight as president of the San Francisco Board of Supervisors announcing the shooting deaths of Mayor George Moscone and Supervisor Harvey Milk, said, “Congress must stop shirking its responsibility and resume a thoughtful debate on gun violence in this country. We must do more to stop this endless loss of life.”