The change in terminology shifts focus from the horror of the shootings to the sadness they have caused. "Massacre" is a dramatic word that evokes slaughter; "tragedy" is more passive, less tied to an individual act. It is, according to dictionary.com's interpretation of the Random House Unabridged Dictionary, "a lamentable, dreadful, or fatal event or affair; calamity; disaster." A massacre, by contrast, is defined as "the unnecessary, indiscriminate killing of a large number of human beings or animals, as in barbarous warfare or persecution or for revenge or plunder."
Many news outlets have been using "massacre," including CNN and Fox News, which have been putting the words "campus massacre" onscreen when discussing the story. CBS News Vice President Paul Friedman, who oversees hard news coverage, declined to comment on the change.