Ukrainian television channel 1+1 claims that among the people who died in the Trade Union Building fire in Odessa there were 15 Russian citizens and 5 citizens of Transdnestria.
If it's true, than depending on a political point of view one may assume that:
A. Russian provocateurs, separatists, spies and other very awful people organized and/or took part in Odessa riots;
B. Ukrainian Ultras have (indirectly, due to сarbon monoxide produced by the fire) killed 15 Russian citizens, who pretty much could be tourists or apolitical bystanders.
If the Russian government assumes that B actually happened, then the Ukrainian government can potentially find themselves in a world of hurt.
It's neither fully A nor B, the people who were killed were certainly not tourists or apolitical, but whether they acted of their own accord or on orders from Russia, or any kind of organisation for that matter, is not clear.
It appears that both sides were armed though.
http://www.theguardian.com/world/2014/may/02/ukraine-dead-odessa-building-fireThe clashes reportedly began after protesters gathering for a rally in support of a unified Ukraine were attacked by pro-Russia activists armed with clubs and air pistols.
But the confrontation quickly escalated into a series of skirmishes as the two sides played a deadly cat and mouse game in the centre of the city.
Police largely stood aside as the two sides hurled molotov cocktails, cobblestones and bricks at each other. Girls as young as fourteen were smashing cobblestones to break them up into missiles of a manageable size.
Combatants on both sides were armed with body armour, helmets and shields and carried baseball bats, chains, metal bars and air pistols.
For two and a half hours the police were absent, said Olga Gold, a teacher watching the unrest. "The authorities have been absolutely indifferent," she said.
Pro-Russia fighters mounted a last-ditch defence of the burning building, throwing masonry and petrol bombs from the roof on to the crowd below.
Medics at the scene said the pro-Russia fighters were also shooting from the roof. At least five bodies with bullet wounds lay on the ground covered by Ukraine flags as fire engines and ambulances arrived at the scene.
If and how Russia will react now remains to be seen. While I wouldn't trust Putin not to invade after the events in Crimea, the release of the OSCE hostages could indicate that Russia uses it's influence to somewhat defuse the situation. On the other hand, if dead Russians are a reason to invade, they have that now, so everything is possible and Putin has proven that he is unreliable and not all that interested in de-escalation.
The Ukrainian public reaction is somewhat understandable in that the government has been perceived as inactive and weak, while these Ultras showed no such restraint. Still it is sad and disgusting that people dying a horrible death is celebrated in such a way, none of this was necessary and it should have been prevented by the police force. It is events like this that might very well drag the country into a civil war, lynching people and producing martyrs is often how these things get started.