If you received a grand jury subpoena or target letter, you need to contact a lawyer. It is that simple.
A federal grand jury is, in essence, an investigative arm of the federal government. Through a grand jury, federal prosecutors can obtain grand jury subpoenas that require people to testify and/or compel people and companies to produce documents and other evidence. The testimony and documents will be used by the grand jury to determine whether a crime has been committed and, if so, who committed it. Thus, a grand jury subpoena or a target letter is a clear indication that a federal criminal investigation is ongoing.
Federal grand juries operate in secret, without the oversight of a judge and without the participation of defense attorneys. For that reason and others, people and companies who receive grand a jury subpoena or a target letter should talk with a lawyer before responding.