The Belgish colonizers were responsible because they promoted a formal and a subsequent socioeconomic differentiation of both ethnic groups.
For example, the Belgish were the ones that included on each person's identity card the ehthinicity that they pertained to, making an official distinction. Moreover they defined the genealogical and physical characters that qualified a person to pertain to each ethinic group. Afterwards, during the genocide, these identity cards were used by the Hutu to identify and slaughter Tutsis.
Moreover, the Belgish considered the Tutsis as more refined and better educated, nearly as Europeans, and they appointed them to occupy most political and economical power positions. Along the years the Tutsis became the elites.
