TODAY | April 16, 2013
>>> as the nation tries to sort through this tragedy, you can't help but remember that a lot of other violent incidents have happened in the month of april. nbc's tom llama s is here right now.
>> we know the last 20 years in this country several terrorist attacks and school shootings have taken place this time of the year, some connected, some random, all of them deadly. as tough as they are to watch, these images coming out of boston are all too familiar. especially during april, which has become a painful and unforgettably violent month in this country's history. six years ago today the virginia tech massacre , 33 people killed on the campus.
>> he killed my best friend.
>> reporter: during another shooting at columbine high school two teenagers killed 13 of their classmates and themselves april 20th , 1999 .
>> let's get out of here. move everybody back.
>> reporter: in 1995 , timothy mcveigh truck bombed the alfred p.murow building. also on april 19th the end of the waco siege in 1993 , after a 51-day standoff, authorities took control of cult leader david koresh 's davidian compound, nearly 19 people died in the aftermath. timothy mcveigh acted in part because of what happened in waco. one more quick note about the timing. yesterday was tax day for everyone in this country but here in boston it was patriots day which commemorates the battles of lexington and concord , the start of the u.s. revolutionary war . big day not only for the country but boston .
>> what was supposed to be a celebration turned out differently.