>>> a member of our family here at nbc news has family roots in chardon, ohio. chris jansing is here with that. listening to you talk about it, it reminded us so much of all the places where we grew up.
>> reporter: anywhere usa. i did grow up near chardon. my brother lives there. i watched fourth of july fireworks in the parking lot of that high school. chardon is smalltown usa, but the question isn't just how could it happen here? it's how do we stop it? even before eric harris and dylan klebold killed 12 class mates and one teacher at columbine high school, experts developed a psychological profile of attackers that is startling consistent. they are almost exclusively boys described after the fact as loners.
>> who seem more isolated by their peers, more withdrawn, lose interest in things that are previously pleasurable to them. they stop being interested in playing the guitar or doing things they liked doing.
>> reporter: the vast majority will never become violent, but these common characteristics are often a first clue that combined with better training of police and school officials led to many plots being thwarted. in 2011, for example, on august 5th near new orleans. later that month in tampa, florida, and in oregon in november. in all three cases, officials were tipped off to disturbing facebook postings and stopped students allegedly planning deadly attacks. january 26, 2012, in roy, utah. a student worried about a text message tipped off police who foiled a bomb plot. clues provided by social media have changed the game, helping identify that rare individual who goes from being disconnected to dangerous.
>> so what kids should do is take head of those warnings. they should go to adults. adults can talk to the kid.
>> reporter: the impact of increased awareness has been significant. in 1992, there were 40 fatal school shootings. in the past seven years, the total number of fatal shootings has been half that.
>> they're in for a tough time in ohio. chris jansing, thank you for that.
