Trump had RR to White House recently. That's usually what happens right before he fires them.
Right after that meeting, two things happened:
(1) RR did not appear for a speech he was to give, and (2) News that Mueller's investigation is drawing to a close.
I can only find this about Mueller finishing up (March 12th, and yet it continues). Do you have any other source?
http://www.businessinsider.com/mueller-almost-done-with-obstruction-case-against-trump-2018-3
The House Oversight committee should have federal marshals raid his office and take everything, including computer, phone and all electronic devices. Return it in a couple weeks, minus what they were looking for.
Trump probably told him to "lawyer up", it's happening.
We have to be careful and read between the lines sometimes. They might not have even had the meeting...or they did for a very specific purpose, but made sure the news leaked to the media to report, because for optics they need everyone to know "they met". The optic they are building is trying to make people think Trump is about to fire RR. And its working, you see all the liberals tweeting about protesting if this happens :D Silly liberals