Which delegate to use to get called when an actor is removed from the scene?

Which delegate to use to get called when an actor is removed from the scene?
I have a weapon spawner actor that will spawn another actor and set itself to its owner. When deleting a spawner actor, I get an editor warning:
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How can I properly handle this situation so that 1) there is no warning when the spawner is removed from the scene, 2) Delete along with the child actor’s spawner.