Neighbors remember seeing few visitors at the single-family house that Pickett had lived in alone since his parents' deaths. He was estranged from his three siblings. After two semesters at West Point, Pickett left the academy in 1972 for undisclosed reasons. He ran into professional trouble as an accountant and was dismissed by the Internal Revenue Service in the mid-1980s. After he was fired, Pickett filed a lawsuit, charging that the IRS had treated him unfairly. When the suit was not successful, he sued his own attorneys. One of his former lawyers said that Pickett filed several dead-end lawsuits. Acquaintances described him as frequently angry at the tax system and the IRS, and a letter he wrote to the agency Friday warns of an impending suicide attempt.

But not every shy loser is a ticking time bomb who will show up at his office or at the White House waving a loaded gun. Pinpointing the most dangerous cases is the specialty of Park Dietz, M.D., founder of the Threat Assessment Group, Inc. His company helps employers identify which workplace grumblers of today might turn into the mass shooters of tomorrow, and how those threats can be neutralized.

Dietz is a widely sought forensic psychiatrist who has participated in some of the more infamous murder and attempted murder cases of the last two decades, including John W. Hinckley Jr.'s shooting of President Reagan, the Menendez brothers case and the O.J. Simpson civil suit. He is also a technical advisor for the acclaimed "snatched from the headlines" crime show "Law and Order."

Thus far, Dietz has found little surprising in the Pickett incident.

What kind of people are likely to threaten the president in this manner?

There are tens of thousands of Americans who have an inappropriate focus on any president, and they communicate their concerns through a wide variety of channels that include letters, phone calls, e-mails, faxes and, less commonly, visits or attacks.

All of those individuals suffer from one or more mental disorders, and the vast majority of them have impaired relationships with their families, neighbors and co-workers. So it's fairly common for those who show up and behave inappropriately, whether violently or not, to have poor social relations and poor work history.

What's the difference between those who threaten from a distance and those who will show up at the White House with a gun?

The most common single difference is being suicidal. One of the problems that the Secret Service and other law enforcement agencies have to cope with is that some suicidal people choose them as a method to commit suicide.

It's called "suicide by cop," and every week in the U.S., someone commits suicide by cop or tries to.

Is the psychological profile the same for a person who commits suicide in this manner and someone who commits a mass shooting at the workplace?

The difference is who it is that they blame for their problems. If that blame has been placed on one's employer, then the workplace is appropriate for that retaliation. If the blame has been placed on the government, then it's the White House.

What's common to both types is that such people say that their lives were ruined by the people whom they blamed. Looked at objectively, most of those claims are totally false or a vast exaggeration, and the problems of the shooters' own making are being blamed on innocent others.

You say that those who attempt suicide by cop, those who make threats at the White House and those who commit workplace murders are all mentally ill. How do their illnesses differ?

Suicide by cop cases often happen to be severely depressed. White House cases are often paranoid. Workplace mass murderers are severely depressed and paranoid.

Do stricter standards for involuntary commitment to mental institutions contribute to these problems?

We could not say that the tightening of the standard for civil commitment, which began in the 1960s or '70s, is the cause of these sensational events, though it is responsible for the tribulations for the mentally ill, and is responsible for the increase of homelessness.

However, it does play a role. I remember when I was a resident [1975 to 1978] and we committed about 10 people a night. My supervisor once yelled at me for committing someone who just said he wanted to kill the president.

At that time, we thought that a person dangerous enough to be committed was someone who might hurt someone soon. Now it means someone who has made a direct threat to kill a named person and has brandished a weapon in the last 24 hours.

Salon News A Salon-eye view of the day's news, with investigative reports, analysis and interviews with newsmakers.