发生了什么事情？
现场已被封锁，由武警等把守。[{'character': '现', 'pinyin': 'xian4', 'highest pitch': 11.23, 'lowest pitch': 9.49, 'duration': 0.29, 'prosody hierarchy': 'null'}, {'character': '场', 'pinyin': 'chang2', 'highest pitch': 9.49, 'lowest pitch': 6.7, 'duration': 0.26, 'prosody hierarchy': '#1'}, {'character': '已', 'pinyin': 'i3', 'highest pitch': 8.86, 'lowest pitch': 6.52, 'duration': 0.13, 'prosody hierarchy': 'null'}, {'character': '被', 'pinyin': 'bei4', 'highest pitch': 7.93, 'lowest pitch': 7.15, 'duration': 0.15, 'prosody hierarchy': '#1'}, {'character': '封', 'pinyin': 'feng1', 'highest pitch': 10.15, 'lowest pitch': 7.35, 'duration': 0.24, 'prosody hierarchy': 'null'}, {'character': '锁', 'pinyin': 'suo3', 'highest pitch': 9.94, 'lowest pitch': 4.11, 'duration': 0.32, 'prosody hierarchy': '#3'}, {'pinyin': 'sp1', 'highest pitch': 0.0, 'lowest pitch': 0.0, 'duration': 0.16}, {'character': '由', 'pinyin': 'iou2', 'highest pitch': 8.83, 'lowest pitch': 7.48, 'duration': 0.19, 'prosody hierarchy': '#1'}, {'character': '武', 'pinyin': 'u2', 'highest pitch': 10.69, 'lowest pitch': 8.05, 'duration': 0.23, 'prosody hierarchy': 'null'}, {'character': '警', 'pinyin': 'jing2', 'highest pitch': 8.25, 'lowest pitch': 6.52, 'duration': 0.23, 'prosody hierarchy': 'null'}, {'character': '等', 'pinyin': 'deng3', 'highest pitch': 7.57, 'lowest pitch': 4.92, 'duration': 0.19, 'prosody hierarchy': '#1'}, {'character': '把', 'pinyin': 'ba2', 'highest pitch': 7.43, 'lowest pitch': 4.92, 'duration': 0.24, 'prosody hierarchy': 'null'}, {'character': '守', 'pinyin': 'shou3', 'highest pitch': 5.16, 'lowest pitch': 4.62, 'duration': 0.34, 'prosody hierarchy': '#4'}]