Mass killers often rely on past perpetrators' blueprints

The potential for cultural contagion, many experts say, demands a public health response, one focused as much on early detection and preventive measures as on politically charged campaigns for firearm restrictions. But in some cases, efforts to identify and monitor potentially violent people can raise concerns about civil liberties.

“You’re balancing public welfare and personal privacy,” said J. Reid Meloy, a forensic psychologist in San Diego who consults on threat assessment for schools and corporations.

Some people have also suggested changes in the way the news media covers mass attacks.

“If you blast the names and faces of shooters on news stations and constantly repeat their names, there may be an inadvertent process of creating a blueprint,” said Dr. Deborah Weisbrot, an associate clinical professor of psychiatry at Stony Brook University, who has interviewed hundreds of mostly teenage boys who have made threats.