Russia is using the fatal fire in the Odessa Trade Union Building in a matter right out of the Joseph Goebbels playbook. The Russian claim "Odessa slaughter: How vicious mob burned anti-government activists alive" is a terrific way to get a population stirred up to support an invasion.
On the other side of the coin, the Ukrainian authorities are claiming "pro-Russians accidentally set fatal Odessa fire with Molotov cocktails"
This is one of those cases where perception matters far more than reality. The flames are being fanned for more violence to come. The truth of how the fire was really set is not a very important issue in this propaganda battle.
Odessa could be a flash point for an escalation of the conflict. Ukrainian authorities are unlikely to allow their remaining Black Sea port to fall into the hands of the separatists following the loss of Sevastopol in Crimea. Yet with a majority Russian speaking population in Odessa, the potential for strong separatist opposition is almost certain
Is Russia setting the scene for another invasion of Ukraine?. Time will tell, but more violence in Odessa is a highly likely outcome. And violence in Odessa could be the excuse that Russia utilizes to expand their occupation of Ukrainian territory. They are already using the media to get their populace ready to support an invasion.