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ABC News.com
A brutal shooting spree in Alabama. A mass slaying in a nursing home on a Sunday morning. A bloody rampage at an immigration center.
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.
See: Why? The Alarming Leap in Mass Murders