IT SEEMS, after all, that there were no explosives in the van. Now that the crisis is over, we learn that he was a 66-year-old man, somewhat fuzzy-minded, obsessed by a cause. Perhaps he intended to end the confrontation when he got in the van and attempted to drive off Wednesday evening. But all this, of course, is after-the-fact speculation.

When Norman Mayer drove up to the Washington Monument Wednesday morning and announced to the world that he had 1,000 pounds of explosives in his van and that he was quite ready to blow up everything within a quarter of a mile of the monument, the threat had to be taken seriously. People in this city are potential victims of terrorists every day. We are now searched upon entering federal buildings that we used to think of as our own property. Washington's streets are fair game for protesters and are vulnerable to rioters. We hear of terrorist bombs in Paris, Rome and Belfast, and we don't want that to happen here. We expect our law enforcement agencies to seek to protect us, and on Wednesday they did.

Within hours of the arrival of the van at the monument, police -- with the aid of other city and federal agencies -- had determined its ownership, the identity of the driver and a good deal about his background. Explosives experts accurately identified the device Mr. Mayer was holding and warned that it could in fact be used to activate dynamite. Psychologists and sharpshooters were dispatched to the scene, and for 10 hours a restrained and conciliatory approach was used in dealing with the man. Officials managed to reroute the evening rush hour and evacuate buildings in the affected area without, in either case, causing panic or undue confusion. It is beside the point that the threatener was well spoken or had a reputation for advocating nonviolence and nuclear disarmament. What mattered then was the simple fact that he threatened to perform a crime that endangered lives and that he had given every indication that he would be able to do so.

No matter what the reason was for Mr. Mayer's decision to leave the scene of his holdout, the determination not to allow him to do so was right. A mobile bomb cruising through the city streets is as dangerous to Anacostia and Glover Park as it is to the White House. The least dangerous place in which to stop it was the already cleared monument grounds. It is a great misfortune when someone who is perhaps unbalanced and, in fact, unarmed is killed by the police. But law enforcement officials did what had to be done at the time, as they had throughout the day