It is a pattern that has increased in frequency and is so dependent on media that we can anticipate after each nationally publicized story there will be several more in the weeks that follow. The reason for that is the people who commit these acts are searching for solutions to their dilemmas. When they see a news account of someone doing the things they feel like doing, who seems like them, they identify with such people, and this is part of what causes them to move from inaction to action.
