As the public struggles to uncover the reasons behind the eight seemingly senseless mass murders so far this year, many researchers are working to determine whether this apparent surge in violence indicates a larger trend, and whether to expect more in the months to come.
Mark Kopta, chairman and professor in the department of psychology at the University of Evansville in Indiana, has researched extensively the country's mass killings, which he defines as attacks leading to the deaths of at least five people, including the killer's suicide.
"This is not a savory subject," Kopta said.
But, he added, it may be one that is becoming increasingly relevant to the U.S. public. In a paper to be presented at the annual meeting of the Midwestern Psychological Association in Chicago this month, he found three incidents in the United States fitting this profile between 1930 and 1970. Three more followed over the course of the 1970s.
In the 1980s, however, there were 10 such incidents of mass murder. The 1990s had 17; and, since the new millennium began, there have been 25 such mass murders.
Six of them occurred last year. And 2009 has already topped that with eight such killings.
Police believe Ervin Lupoe of Los Angeles fatally shot his wife, his five children and himself Jan. 27 after faxing a note to a local television station claiming the couple had just been fired from their hospital jobs. A Cleveland man, Davon Crawford, killed his newlywed wife, his sister-in-law and three young children March 5 before shooting himself to death when cornered by police.
The four mass shootings in March made it the bloodiest month yet this year. Michael McLendon of Kinston, Ala., killed 10 people -- five family members and five other people -- before committing suicide March 10 in a factory in which he formerly held a job. Guillermo Lopez of Miami opened fire at a party March 15, killing his estranged wife and three other people before returning to his apartment, setting fire to it and shooting himself.
Five days later, Robert Stewart entered a nursing home in Carthage, N.C., March 20 and opened fire on residents, killing seven of them along with one nursing home employee. And Devan Kalathat, an engineer at Yahoo living in Santa Clara, Calif., fatally shot his two children and three other relatives March 29 at a family party before turning the gun on himself.
The first six killings set the stage for two more tragedies so far this month, the first an April 3 rampage in which Jiverly Wong entered an immigration center in Binghamton, N.Y., armed with two handguns. Police told the Associated Press that the man fired 98 shots, killing 13 other people before taking his own life.
The country's latest mass shooting occurred in the early hours of Saturday morning, when James Harrison of Graham, Wash. killed his five children before driving to a nearby casino and shooting himself inside his car. Authorities told the Associated Press that Harrison committed the murders after he learned from his wife that she was planning on leaving him.