The article does not say why but if you read it I think you can figure it out.
http://www.foxnews.com/us/2017/04/26...-counties.html
The Crime Prevention Research Center (CPRC) said in a new report that there is a “geographical concentration” of murders, with 68 percent of killings occurring in just 5 percent of the nation’s counties. The homicides also tend to be concentrated to relatively small pockets of those counties, the report said.