I confess my ignorance, but how could two ethnic groups live side by side for years in harmony and then go on a crazy killing spree. What happened in the breakup of the old Soviet Union to create this catastrophe?
It may seem odd to a peaceful person, but the latent tensions can exist for centuries. Consider Yugoslavia, when it was held together by strongman Tito, versus the inter-state strife that arose in the Balkans after Yugoslavia broke up. Bosnia, Kosovo, Serbia... it was a religious war, for the most part.
The Soviet Union was held together by force. They weren’t living in harmony, they just knew if they didn’t pretend to get along the hammer would come down, hard. Then the hammer evaporated.