Question: who was the first president killed in office
[{'answer': 'Abraham Lincoln', 'provenance': [{'wikipedia_id': '13434603', 'title': 'List of Presidents of the United States who died in office', 'start_paragraph_id': 2, 'start_character': 308, 'end_paragraph_id': 2, 'end_character': 323, 'bleu_score': 1.0, 'section': 'Section::::Abstract.'}]}]