Contrary to Dr. Bushman’s suggestion, violent video games are not a commonality among mass homicide perpetrators. The impression that a link exists is a classic illusory correlation in which society notes the cases that fit and ignores those that don’t. When a shooter is a young male, the news media make a fuss over violent video games, typically forgetting to inform the public that almost all young males play violent video games. Thus, finding that a particular young shooter happened to play violent games is neither surprising nor meaningful.

However, we’ve seen a rash of high-profile gun violence committed by men over the age of 60 (William Spengler, Douglas Harmon, Jimmy Lee Dykes, etc.) in past months. Since these incidents don’t fit the common social narrative of the mad gamer, they are simply ignored. 
Christopher J. Ferguson, CNN.com.