One Big Happy Family

I can't find an actual set of cases this was based on, but certainly there have been cases of spree killings associated with robberies and car thefts. Slim Pickets and Bo Hopkins, normally cast in endearing or heroic roles, are the men in the family, and do the actual killings. The matriarch orders the killings, the son's girlfriend (or wife) helps set some of them up, and a distressed teenage girl follows along in silence.

5-0 uncovers that this family has killed dozens and dozens of people across the country, each crime collected a very few hundred dollars or less. Their complete sociopathic nature is chilling, and that kind of evil DOES exist in the world.