turn on sb to criticize or physically attack someone suddenly 突然指责某人；突然袭击某人：All of a sudden,the dog turned on him and bit him.突然，那条狗扑上去咬他。（摘自《朗文多功能英汉双解词典》第五版）Why are you turning on me (= criticizing or blaming me)? 你们怎么突然都冲我来了？（摘自《牛津高阶英汉双解词典》第8版）

    He turned on the policeman swiftly and fiercely.的 turned on 也应该是上述意思，不是转身，面对的意思。