The kidnappers were abducting the businessman in a black van by force.

abducting 是动词 abduct 的现在分词形式。abduct 由前缀 ab-（表示"离开"）和词根 duct（引导）组成，字面意思是"强行带走"，特指"绑架、劫持"的行为。 by force 是一个固定短语，force 指"武力、暴力"，by force 表示"通过暴力手段、强行地"。