Letter to the Hon. Robert O'Brien, Assistant to the President for National Security Affairs, the Hon. Mark Esper, Secretary of Defense, the Hon. Michael Pompeo, Secretary of State, and the Hon. John Ratcliffe, Director of National Intelligence - After Closed "Briefing" on Alleged Russian Bounties Targeting U.S. Troops, Warren and Hirono Seek Answers from Trump National Security Adviser, Secretary of Defense, Secretary of State, & Director of National Intelligence