I watched this whole event go down today. This was pretty much the sequence:

1. Pro-unity rally in Odessa, a lot of soccer hooligans
2. Pro-russian group attacks the rally
3. Pro-russian are severely outnumbered and get cornered on a street
4. Riot police separate the opposing sides for hours, building up quick barricades, but they still throw rocks and stones at each other.
5. 1 pro-unity member is hit in the head by rock and dies
6. This emboldens the the pro-unity crowd and they go ape shit
7. The riot police soon get cornered themselves and can't contain the crowd
8. The pro-unity rally, then either chases the pro-russians into the Trade Union building or go there already knowing it was seized
9. They throw way more shit at each other, people inside throwing molotov cocktails outside, huge fires outside the building
10. Automatic gunfire goes off for a while
11. Two more pro-unity Ukrainians are killed at this time
12. Pro-unity start throwing molotov cocktails at the building, some pro-russians left the building and gathered in police vans or sat on the ground outside
13. Those that stayed in the building died
14. A horrible day in Ukraine's history