Called is the best answer. What did he do after he saw the theft? He called the police.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.
wisdom27He called the police after he had seen a thief.It's fine.
wisdom27Are they both correct?Yes, both are correct. The past perfect is mainly used to reduce a possible confusion in the time-order of two past events. It is not a "rule" that it must be used. It is primarily used in narratives (stories) about the past. It is often the writer's choice to use the past perfect or not.