I am writing a character monologue from the perspective of Boo Radley after he saves Jem in To Kill a Mockingbird. What tense should I use?It says after he saves, so is it past tense?
Even though you are communicating the action that happened after Boo's encounter with Bob Ewell, you do not necessarily have to use a past tense monologue. You could have Boo describe the events as if it were happening at that moment.
"I am watching the children pass through the darkness, and I see a man stumbling after them. I wait until they nearly pass me, and then I see that he is about to attack them. I move forward..."
You could create a monologue with Boo giving a statement to Sheriff Tate where he describes what happened from his point of view. I think a past tense monologue would be easier, but a use of present tense might be more interesting and challenging.