The information you're trying to delete is not deemed speculative by the document and is corroborated by an Azerbaijani civilian at the scene as noted in the document. If you need any more corroboration, then see the Shelling of Stepanakert article. Mass killings are defined as mass murder. As already explained, murder requires premeditation. These deaths occurred during "chaos" while the Battle of Khojaly was being faught. It is very tragic, but not murder.