"If brutal killers like these two are at work, it is no wonder that so many people have fled," he said.

no 是否定词，表示"没有"或"不"。 wonder 是名词，意思是"惊奇、疑惑"或"奇迹"。 no wonder 是一个固定短语，表示"难怪、不足为奇"，用来表达对某种情况或结果不感到惊讶。