They were backed by Russia obviously, it doesn't matter in this context, every civil war is backed by someone. By the way, Russians and Ukrainians are still continuing to put military targets in civil settlements. They bomb them, killing and wounding civilians, sometimes even themselves by misfiring anti-ballistic missiles, and blame each other for war crimes.
Did Ukrainian army shell Ukrainian citizens while trying to shell rebels in 2014? Definitely, and not once, that shitty story with an air-conditioner for example:
https://www.cnn.com/2014/06/03/world/europe/ukraine-luhansk-building-attack/index.html
That was the question, and the answer is yes.