Because of the high crime rate in the Washington, D.C. area (Crime rate peaked during the 1990's), D.C. was given the nickname "Murda Capitol".
Sam: Man i bet D.C. is safe as hell
Bryant: Don't you know?
Sam: Know what?
Bryant: Man thats Murda Capitol, fuck around and get your ass shot thinking like that!
Police officers, five-0, law enforcement
"Better lay low son, your boys riding around on bikes"