"[Victimization] is not simply a function of spatial proximity or of individual risk factors such as age, race, gender or gang affiliation, but also of how people are connected, the structure of the overall network, the types of behaviors occurring in the network and an individual's position in the overall structure,"Via NPR
What I found especially interesting was that your place in these social circles trumped gang membership, drug dealing, etc. for determining how likely you were to be murdered. In essence, the closer your relationship is to a murder victim, the more likely you yourself are to also become a victim.
I also found it encouraging that Chicago PD was using this theory to try and intervene with those at risk for becoming the next murder victim. Given Chicago's reputation regarding murders, this is worth trying.