Read the Trump Administration’s Warning Letter to Laura Cooper - NYTimes

The White House has declared that the executive branch will not cooperate with the House’s impeachment inquiry, but some officials have nevertheless provided testimony to Congress about what they know about whether President Trump’s attempts to pressure the Ukrainian government into investigating his political rivals were a quid pro quo in return for aid. One such witness, Laura Cooper, a Pentagon official, received a warning letter that shows how the administration has attempted to persuade officials to keep silent. ....
https://www.nytimes.com/2019/10/24/us/politics/laura-cooper-pentagon-letter.html