The diplomatic aide who reportedly overheard a phone call in which President Donald Trump asked the EU ambassador about “the investigations” is set to testify in the House’s impeachment inquiry Friday.

Acting Ukraine Ambassador Bill Taylor delivered bombshell testimony Wednesday, telling the House that one of his aides who was accompanying EU Ambassador Gordon Sondland during a Ukraine trip overheard Sondland on the phone with Trump on July 26.

The aide told Taylor that Trump could be heard through the phone asking Sondland about “the investigations,” Taylor testified. Taylor later said he understood “the investigations” to be the same ones Trump and others repeatedly pushed Ukraine to pursue: probes into the Bidens and the 2016 U.S. election.

The call took place after Sondland met with an aide to Ukrainian President Volodymyr Zelensky, Taylor testified, and a day after Trump pressed Zelensky for investigations in a phone call.

“Ambassador Sondland told President Trump that the Ukrainians were ready to move forward,” Taylor testified. After the call, when the aide asked Sondland what Trump thought about Ukraine, Sondland told the aide that Trump “cares more about the investigations of Biden” than Ukraine, Taylor testified.

CNN and NBC News reported that the aide who relayed the information to Taylor is David Holmes. The U.S. embassy in Ukraine currently identifies Holmes as a counselor for political affairs.

Midway through Taylor’s testimony Wednesday, the impeachment inquiry announced that Holmes would deliver testimony in a closed-door hearing on Friday.