The man pretending to be a philanthropist was actually a deceiver who targeted elderly people.

deceiver 是动词 deceive（欺骗）加后缀 -er 构成的名词，表示"实施欺骗行为的人"，即"骗子"。deceive 本身由前缀 de-（表示"向下、负面"）和词根 -ceive（来自拉丁语 capere，意为"拿取"）组成，字面意思是"用不正当手段获取"。