Yes it could be an accident or degraded from previous fighting.

But you are ignoring that Russia is responsible for it as an occupying power under the Geneva convention. Blame falls on them then in all instances.

Then you have a member of the Russian Duma bragging about it on TV- not proof Russia did it but proof of Russia's attitude to it.

Furthermore you have Russia continue to shell and fire upon rescue workers and do little to help the people flooded out in the territory that they consider now 'part' of Russia.

Of course, you didn't have to write that long response, you could have just said "Russia never does anything like this, only Ukraine" and left it at that. )