In America's second multiple shooting in 24 hours, the gunman killed two men and wounded two others in an unexplained boatyard attack. On Tuesday, seven died when a worker opened fire on colleagues in an office meeting in Honolulu, Hawaii.
Citing the statistic that 13 children are shot dead every day in the US, Mr Clinton said: "I don't think we understand fully just how much more violent the United States is than other countries."
Seattle's police chief, Norm Stamper, said extra officers would be put on duty to find the killer. Although there appeared few clues to his identity, police said they had received many tips. "We have a handful that look pretty good at this point," said Chief Stamper. But publicly, at least, the police had no theory about the deaths.
The gunman, described as a white man in his thirties, walked calmly into a boat repair shop, shot four men with a 9mm pistol, and disappeared. A police dog apparently picked up his scent but lost it. The police pulled in a suspect but soon released him. The boatyard is located in a busy commercial district and the gunman simply vanished into the crowds.
As night fell yesterday, Seattle's mayor, Paul Schell, asked the public to be wary. "Check on your neighbours, check on senior citizens, check on your premises," he said. Local schools were shut down in the immediate aftermath, but reopened yesterday.
The killer seemed not to know the victims; at least, they did not know him. But he walked straight to the office where the shooting took place and left immediately afterwards, suggesting he knew who he was after.
The dead were named as Peter Giles, 27, and Russell Brisendine, 43. A 58-year-old man shot once in the chest was reported to be in a serious condition, while a 19-year-old man shot in the arm was satisfactory.
Mr Giles, the shipyard manager, was "just a super young fellow", said his grandfather, Richard Kelly. "Who would expect a decent, law-abiding, wonderful citizen to just get shot in cold blood?"
The police called in armed assault teams, helicopters, armoured personnel carriers and dogs as the hunt continued last night, but they acknowledged the trail had gone cold.
President Clinton's warning was seen as an attempt to revive the debate on gun control. "Our nation continues on this day to be reminded of the horrors of gun violence. We need to do more to keep guns out of the hands of criminals and children," he said. "Congress needs to send me common- sense [gun] legislation."
The issue may become more important as campaigning for the 2000 presidential election begins in earnest. So far each incident has sparked horror and calls for new gun laws, but interest has soon subsided.
Deborah Orr, Review page 5