Instead of hiding the player until they do something wrong, probably better for the player to “broadcast” their action to nearby pawns.
Like, if you have a “steal item” function or whatever on the player, have it sphere trace for pawns and call a function on them (or use an interface message) to let them know they witnessed a crime or whatevs. This function would then decide how to react, and add the player as a target on the AI’s behavior/state tree if the action should aggro them.