We use data of neighborhoods of Bogotá to assess the causal relation between their adolescent fertility and their homicide rates. We find that neighborhoods with high adolescent fertility rates, and that have low secondary enrollment and high crime rates at the moment the children of their teen mothers become teenagers, are more likely to have higher homicide rates in the future, when those children reach their peak crime ages, estimated to be between 18 to 26 years old in violent cities of Colombia. The result is robust to various specifications, and to modeling the spatial autocorrelation of homicides.