Of the rampage killers who were over 25, a third had college degrees.

The rampage killers were overwhelmingly male - but not entirely.

The rampage killers were far more likely to have a military background, and to kill strangers.

It also found that rampage killers share several traits.

Although these shootings seem new, the Times study shows that teenage rampage killers were around far before the recent trend.

Many rampage killers are extremely difficult to treat, say psychiatrists who have interviewed them.

The racial profile of the rampage killers is close to that of the entire population.

The rampage killers in the study, young and old, often talked for months in advance about their murderous plans.

Here again, however, was a distinction from regular murderers, who are about twice as likely as rampage killers to be women.

Mr. Wallace, like other rampage killers, was convinced he was defending himself against an intricate conspiracy.

TODAY - A portrait of the nation's rampage killers over 50 years.

TODAY - One father's efforts to understand his son's murder by a rampage killer.

And now, rampage killers opt to off themselves instead of waiting for the justice system to do it for them, with murder suicides constantly in the news.

Across the country, other families whose loved ones have been killed or wounded by rampage killers also try to find a place in their lives for the shattering events.

Another term, rampage killer, has sometimes been used to describe spree killers, but it does not differentiate between mass murderers and spree killers.

Mark O. Barton, a rampage killer in Atlanta, was reported to have singled out day traders because he had suffered huge losses in the market.

The rampage killers were older than regular murderers, with more in their 40's and 50's and fewer in their 20's, compared with the typical killer.

After this shooting (and most school and workplace rampages, big and small), forensic experts quickly and properly cautioned that no profile of a rampage killer exists.

As to whether they have ever stopped a rampage killer, Mr. Garahan said: "You do this stuff and you don't know whether you prevented something or not.

To the Editor: "The Well-Marked Roads to Homicidal Rage" (front page, April 10) points out many warning signs of rampage killers.

The last speaker was a dignified woman who said her family had been identified to the rampaging killers as Tutsis by Hutu neighbors whose children had played with hers for years.

They are chosen for their mental stability, while rampage killers are typically mentally troubled, said Dr. Jerrold Post, a psychiatrist who directs the political psychology program at George Washington University.

To the Editor: Your April 9-12 front-page series "Rampage Killers" supplies a factual baseline from which to consider the recent school shootings and brings due attention to the understudied issue of violence committed by women.

To the Editor: Regarding rampage killers, you say (editorial, April 13) that "cultural influences on this group, such as violent entertainment, seemed to have little impact," and you focus instead upon mental health problems and gun control.

To the Editor: Re the April 9-12 front-page series, "Rampage Killers": While a tiny minority of people with psychiatric disabilities commit violent crimes, there are millions of us who are trying to lead productive lives.