He won't fire any of them during impeachment even if it's suspected they are lying. (I am not saying any are as the whole process isn't over) Vindman on the other hand is a national security threat, he's lost the confidence of his co workers many whom testified they've found it necessary to leave him out of the loop and the fact that he's been asked numerous times to head up the defense forces of Ukraine leaves it highly questionable why another country feels comfortable trying to hire him and what is he doing exactly to make them feel that comfortable. I wouldn't fire him during impeachment but he'd be first on my list out the door afterwards if I had it within my authority as president.