There were reports that a lion had escaped from its cage at a nearby zoo.

escaped 是动词 escape 的过去分词形式。escape 由前缀 es-（表示"向外"）和拉丁词根 cape（意为"抓住"）组成，字面意思是"从抓住的状态中出来"，即"逃脱、逃离"。在这里 escaped 表示"已经逃出"的动作状态。