"they'll shoot me i don't care they'll shoot me in the back of the neck i don't care down with big brother they'll always shoot you in the back of the neck i don't care down with big brother" (George Orwell, 1984)
This is a citation from George Orwell's 1984, a dystopian novel which centers on the government overreach, totalitarianism and repression in all forms towards the society as a whole.
In the novel, there is a superstate called Oceania, ruled by the Party who employed the Thought Police, whose job is to persecute individuality and independent thinking.
Thoughtcrime represents person's unorthodox thoughts in the political sense, doubts that contradicts the rules of the Party. These thoughts are contrary to accepted norms of society.
Those who commit Thoughtcrime (think negatively about the Party) will be punished by death. The accused criminal is abducted at the night and disappear entirely. He is never heard or seen ever again. All documented history about that person is erased, as well. The aforementioned citation is a thought from the main character Winston Smith.