There have been several cases of deadly incidents involving police and African-Americans this year. The killing of 18-year-old Michael Brown last August fueled racial tensions. Police officer Darren Wilson said he feared for his life after Brown attempted to take his gun. Last month, an Ohio police officer shot and killed a 12-year-old African-American boy. ___________________今年已经发生了数起涉及警察和非裔美国人的死亡案例.今年8月,18岁的Michael Brown之死使得紧张的种族关系火上浇油.警察Darren Wilson表示,在Brown试图抢夺他的枪之后,他感到自己的生命受到威胁.上个月,Ohio州一位警察开枪打死了一名12岁的非裔男孩.________________________