I certainly find it odd that 3 adults planned, coordinated, and executed this crime. The rape of the woman and the killing of the man would indicate that a message was sent. Hard to believe that this was random.
This was totally random, and totally typical of crime in DC. Those guys were cruising Gtown looking for someone to rob. The rape was an unexpected bonus for them. They are without doubt products of the DC schools, which means functionally illiterate, and mean little sociopathetic bastards. All last summer, gangs from the same socio-economic group were criusing the National Mall doing the same thing. They cracked down on them because it has "harming tourism." This is par for the course in DC, and nobody thinks anything of it. The "community" views the perpetrators as victims of a racist system. Read the paper here for a couple of months and weep. There is a reason why Georgetown declined the privilege of having Metro run out to M Street and Wisconsin.