Another one: https://www.palmerreport.com/opinion/chuck-grassley-dianne-feinstein-trump-russia/1942/

If Comey’s briefing had been insufficient, Grassley and Feinstein would both have looked angry and defiant, and they’d have said so. If Comey had given them some evidence that Donald Trump was innocent on Russia, then Grassley would have looked relieved. But the news they received in that meeting was visibly devastating to them both. So much so that the usually talkative Grassley couldn’t muster a word. Feinstein was even making a point of protecting Grassley from having to speak at all, as if she knew that he was in an even worse headspace than she was.

There’s only one scenario that could have produced that result: James Comey briefed them on evidence so grave and so damning about Donald Trump and Russia that they both just realized the fate of nation now hinges on their ability to come together and handle it correctly.

Think i'd come up with a couple of more scenarios what might've made them shook.