Maybe this death is not related to previous assasinations of separatists leaders, but still, it looks very strange to see so many deaths in short period, even if it's not related.
And as I know, any sides in this war Ukraine, Russia) don't have biological weapons. Even if they would have, I don't think they would use it.
It seems that the rebels are honoring the ceasefire, while the Kiev junta is ambushing the rebel leaders. This can get ugly, if the rebels decide to retaliate and start assassinating the pro-Kiev figures in the government controlled part of Donbass.