My great uncle, his wife and son were all gunned down in cold blood back in 1963.

[Atypical Liberal]

30. Tragic, but fortunately, rare.

The idea that most homicides are committed by people who "just snap" is a myth. Criminologists know that most people who commit homicide have extensive prior criminal histories. And this should not be surprising. Few people develop a callous disregard for the lives of other people overnight. Rather, it is usually years of escalating victimization and violence that culminates in murder.

http://www.cardozolawreview.com/index.php?option=com_content&view=article&id=138:kates201086&catid=20:firearmsinc&Itemid=20

"In 2009 Clayton Cramer and I published an article21 describing some of the studies subsequent to those Professor Elliott summarized. Like the prior studies, the later ones continue to demonstrate his point that “virtually all” murderers have prior criminal records. A few examples:

MASSACHUSETTS: “Some 95% of homicide offenders . . . [in a Kennedy School study had been] arraigned at least once in [Page91] Massachusetts courts before they [murdered]. . . . On average . . . homicide offenders had been arraigned for 9 prior offenses.22

ATLANTA: Eighty percent of 1997 Atlanta murder arrestees had previously been arrested at least once for a drug offense; and 70% had three or more prior drug arrests—in addition to all their arrests for other crimes.23

DELAWARE: Reporting on shootings, including many in which victims had only been wounded rather than killed, 80% of shooters had arrest records going all the way back to their juvenile years; 57% had been charged at least twice with drug offenses.24

NEW YORK CITY: A New York Times study of the 1,662 murders in that city over the years 2003-2005 found “[m]ore than 90 percent of the killers had criminal records . . . .”25

ILLINOIS: Over the years 1991-2000, the great majority of murderers had prior felony records.26"

The single biggest determinating factor in whether someone is going to commit murder or not is their past criminal history. If they have no criminal history, they are extremely unlikely to commit murder. It does happen as happened to your family and to those families in the recent mass murder, but fortunately, it is rare.