Sen. Rand Paul (R-Ky.) blasted the past administration on Wednesday, May 13, after it was revealed that top Obama officials had requested the unmasking of then-incoming National Security Adviser Michael Flynn.

“This is incredibly troubling and shocking, that the previous administration, under President Obama, under Vice President Biden’s specific instruction, was eavesdropping on an American—an American adviser to the next president,” Paul said. “If Vice President Biden and the president’s inner circle of advisers were all listening to a senior Trump adviser’s personal phone conversation, this would amount to a serious abuse of power. The only question remains is ‘What did President Obama know, and when did he know it?’”

Acting Director of U.S. National Intelligence Richard Grenell on Wednesday released a declassified National Security Agency document showing that senior Obama administration requested to unmask Flynn’s identity. The document includes then-Vice President Joe Biden, then-FBI director James Comey, former Director of national Intelligence James Clapper, and former CIA Director John Brennan.

“It looks like each of these administration officials actually individually requested to listen to this conversation,” Paul said. “These rumors have been going around for years that President Obama’s administration was abusing this power of unmasking and this sounds like they were abusing it to go after a political opponent, which I think is a very serious offense and should be investigated.” 

On Twitter, Paul called Biden, Clapper, Comey, Brennan to testify under oath, asking, “What did the former president know?” 

Fox News last week reported that Obama was aware of Flynn’s intercepted phone calls with then-Russia Ambassador Sergey Kislyak during the presidential transition period. During a Jan. 5 meeting in Oval Office, Obama said he had “learned of the information about Flynn” and his conversation with Kislyak about the sanctions. 

Paul announced that he invited Grenell to testify before the Senate Subcommittee on Government Oversight next week about the unmasking of Flynn, noting that he has questions about what Biden and Obama knew.