Remember the saying that the spouse is almost always the one who committed the murder? Or the fear that people should have of family members who might harm you?
Take the breakdown of the 16,272 murders in 2008.
Family current of past, immediate family or not
9.4% are murders committed by the Husband, Wife, Common-law Husband, Common-law Wife, Mother, Father, Son, Daughter, Brother, Sister, In-law, Stepfather, Stepmother, Stepson, or Stepdaughter.
1.8% are other family members
Even these murderers are not your typical family members and are very likely to have criminal records.
If you make it broader to include former family or other relationship, you get.
4.2% are boyfriend, girlfriend, ex-husband, or ex-wife
Non-family, no emotional relationship murders
14% Acquaintance murder (this is a very broad category that includes everything from prostitute and johns to taxi cab drivers and their fares)
5.2% Other Known
11% Stranger murder
39% Unknown relationship (note these murders are very likely to involve gang fights to others where there is no direct relationship between the victim and criminal)
If you are worried about job related murders either on or off the job, stop worrying. In 2008, there were a total of 14 murders committed by an employee or an employer. That accounts for only 0.086% of the total.
The rate of homicides committed by whites and blacks.
Any how the people tend to overwhelmingly kill people of their own race.
Also of interest is how rare mass murders are.
See also here for data.