NEW: Trump fired inspector general as he was probing his administration's potentially illegal sales

President Trump's abrupt decision to fire the inspector general of the State Department is now making more sense.

According to two sources with NBC News' Josh Lederman, “Linick was also investigating use of emergency declaration last year to sell arms to Saudis over objections of Congress” at the same time Trump let him go.

The information was confirmed by a member of Congress.

"I have learned that there may be another reason for Mr. Linick’s firing,” Rep. Eliot Engel (D-NY) told Washington Post's Greg Sargent. “His office was investigating — at my request — Trump’s phony declaration of an emergency so he could send weapons to Saudi Arabia.”

The State Department was also briefed on his findings but a report has not been made public yet.

“We don’t have the full picture yet, but it’s troubling that Secretary Pompeo wanted Mr. Linick pushed out before this work could be completed,” Engel said further.

The decision of President Trump to sell $8 billion to the Saudis caused major upheaval on Capitol Hill. The House voted to block it but it only went through on "emergency" powers rarely used under the Arms Export Control Act when national security is being threatened, and without congressional approval. Democrats as well as Republicans roundly opposed the deal.

What would happen if it was discovered there wasn't really an emergency? Well, let's just say it just wouldn't be good for Trump in an election year.