Question: who let the walkers in the prison in season 3
[{'answer': 'an unidentified individual', 'provenance': [{'wikipedia_id': '37209922', 'title': 'Killer Within', 'start_paragraph_id': 3, 'start_character': 20, 'end_paragraph_id': 3, 'end_character': 46, 'bleu_score': 1.0, 'section': 'Section::::Plot.\n'}]}, {'provenance': [{'wikipedia_id': '37209922', 'title': 'Killer Within', 'start_paragraph_id': 3, 'start_character': 0, 'end_paragraph_id': 3, 'end_character': 148, 'bleu_score': 0.9214109120166031, 'meta': {'yes_no_answer': 'NONE', 'annotation_id': 17103338748234313169}, 'section': 'Section::::Plot.\n'}]}]