No police tragedy is worse than the death of Officer James Gordon, shot and killed in his own home by another police officer who reportedly mistook him for an armed burglar.

Officer Gordon's death should not be a time for finger-pointing and divisiveness. It is, as Prince George's County States Attorney Alex Williams recognizes, a time for careful and objective investigation to resolve any doubts about how and why Gordon died. Regardless of what Williams may find, it is also a time for police to ensure that Gordon is the area's last police officer -- or armed citizen -- to die as he did.

There are two lessons in Officer Gordon's legacy to the Washington area. The first is that any citizen attempting to protect his home by picking up a gun could die just as Gordon did. Gordon's death is a cruel reminder that the best way for citizens to protect themselves and their homes from intruders is to leave as quickly as possible and to call the police from the nearest telephone. Gordon's death should tell citizens that 911 offers them much more protection than does a .38.

But James Gordon was not just any citizen who picked up a gun to protect his home. He was a trained police officer who, by all accounts, served this community in an exemplary fashion for 17 years. The population of this community -- Washington, and its Maryland and Virginia suburbs -- almost certainly includes more law enforcement officers per capita than any other metropolitan area in the country. The number of law enforcement agencies here is also staggering. In my American University classes, D.C. police have rubbed elbows with law enforcement officers and agents from Fairfax County, Fairfax City, Falls Church, Arlington County, Montgomery County, Prince George's County, Alexandria, Rockville, Takoma Park, the U.S. Capitol, the Secret Service, the FBI, the State Department, the U.S. Park Service, the Drug Enforcement Administration and too many other jurisdictions to list.

All these officers and agents are trained and expected to take action when they see crimes or trouble. That is a mixed blessing. Because they are so great in number, these officers and agents probably prevent and interrupt a lot of the street crime found in other places. But they have not eliminated it, and their great numbers mean that they are bound occasionally to run into each other in dangerous situations. Therein lies the second lesson of the tragedy that befell James Gordon: unless these agents and officers can tell the good guys from the bad, some are also bound to die in -- and to live with -- tragedies like the one that occurred in Gordon's home.

It is easy to identify the good guys when they wear uniforms. Like Officer Gordon, however, off-duty officers -- and on-duty investigators -- look like the rest of us and, with gun in hand, are hard to distinguish from the bad guys. We found that out a decade ago in New York, where, in five years, police shot at other officers in nine situations like the one in which Officer Gordon died. In every one of these cases, the scenario was the same: officer in plainclothes witnesses or hears about crime, draws gun and tries to apprehend suspect; uniformed officers hear about crime from their radio dispatcher, respond, see a man with a gun and shout at him; he instinctively turns toward the noise; uniformed officers, seeing his gun pointed at them, shoot; too late, they find that they have killed a cop.

These tragedies don't occur in small towns because police and other law enforcement agents in such places all know each other by sight and by name. Still, these shootings ceased in New York when all the law enforcement agencies in the area stopped pointing fingers. Together, they ended these tragedies by training all their officers to use the same words -- Police! Don't move! -- when challenging armed people. All officers are also trained to freeze and to slowly identify themselves when challenged with these words. Every cop and law enforcement agent in the New York metropolitan area had these three words implanted in his or her mind, and no cop has since been shot at by another good guy. That is not so in this area.

All the facts of James Gordon's death are not in, and I have spent too much time in patrol cars to prejudge police or their actions. But I do know that he will not be this community's last cop to die at the hands of another officer unless our police and law enforcement agencies devise some way to give the good guys a chance to identify themselves in circumstances like those in which Gordon died. The Washington Metropolitan Council of Governments might begin this process by calling a meeting of the heads of all the federal, state, county and municipal law enforcement agencies in this community. Once together, these officials should not be permitted to adjourn until they have agreed upon a program that will protect our officers from each other.

We should all mourn James Gordon, but the best way to honor his memory is to insist that three simple words -- Police! Don't move! -- be engraved upon the memory and in the training of every law enforcement officer and agent who is permitted or required to carry a gun in this community. Failing to do so is a disservice to Gordon and to all the men and women who police our streets. -- James J. Fyfe is a professor of justice at The American University and a former lieutenant in the New York City Police Department, where he served 16 years. this will break differently.