Special counsel Robert Mueller has impaneled a Washington, D.C., grand jury for his probe of Russia’s interference in the 2016 election, a person familiar with the case told The Daily Beast. This latest development, The Wall Street Journal first reported, is “a sign that his inquiry is growing in intensity and entering a new phase.” Some of the documents included in the subpoena concern Donald Trump Jr.'s meeting with a Kremlin-connected Russian lawyer at Trump Tower in 2016, CNN reported, citing a source familiar with the matter. The subpoena also seeks testimony from people who were present at that meeting. President Trump’s lawyer Ty Cobb said in a statement: “Grand jury matters are typically secret. The White House favors anything that accelerates the conclusion of his work fairly.…The White House is committed to fully cooperating with Mr. Mueller.” The president, however, has repeatedly called Mueller’s investigation a “witch hunt” and has publicly called into question the former FBI chief’s credibility as an impartial investigator.