Yes, this was honestly surprising but not impossible. The observations about wars in the past is that about 80% of soldiers have problems shooting somebody at point blank. But among the 20% remaining you got people who don’t care, are sadists or otherwise don’t care. In short there are always someone ready and willing to kill other human beings.

We can also use WW2 as an example. German commanders ordered their soldiers to gun down Jews repeatedly. However this took such a mental toll on regular soldiers that German officers noticed it reduced the fighting ability of their soldiers. Concentration camps got built in part to relieve German soldier of the trauma of killing innocent civilians. Not because the third Reich cared about the Jews killed but because they cared about their own soldiers.

Likewise it could potentially take a mental toll on Russian soldiers to be ordered to kill civilians unless those who are sadists do it.

Now Russians superiors may not care as they have historically not cared much about the welfare of their own soldiers.

Another possibility is that the killing of civilians happened for similar reasons as why American soldiers massacred civilians in Vietnam: They had taken heavy losses and were under a lot of stress. Soldiers who have seen a lot of their comrades die often end up taking out their anger on innocent people.

It may simply be an expression of a mental and moral breakdown of Russian forces after too much failure and heavy losses.

Until further investigations have happened I guess we will not know if this was part of a deliberate terror wave, sadism or lashing out against civilians due to their own losses and failures.