Question: who's the killer in the killing season 4
[{'answer': 'Fielding', 'provenance': [{'wikipedia_id': '41862975', 'title': 'The Killing (season 4)', 'start_paragraph_id': 28, 'start_character': 330, 'end_paragraph_id': 28, 'end_character': 338, 'bleu_score': 1.0, 'section': 'Section::::Development and production.:Casting.\n'}]}, {'answer': 'Knopf', 'provenance': [{'wikipedia_id': '41862975', 'title': 'The Killing (season 4)', 'start_paragraph_id': 28, 'start_character': 320, 'end_paragraph_id': 28, 'end_character': 325, 'bleu_score': 1.0, 'section': 'Section::::Development and production.:Casting.\n'}]}, {'answer': 'Rayne', 'provenance': [{'wikipedia_id': '41862975', 'title': 'The Killing (season 4)', 'start_paragraph_id': 28, 'start_character': 186, 'end_paragraph_id': 28, 'end_character': 191, 'bleu_score': 1.0, 'section': 'Section::::Development and production.:Casting.\n'}]}]