Potentially bombshell testimony in the impeachment inquiry came from an unexpected source Friday. David Holmes, an aide to top U.S. diplomat in Ukraine William Taylor, said in private testimony that he overheard President Donald Trump and the U.S. envoy to the European Union, Gordon Sondland, talk about Ukraine in July. Holmes says he was at a restaurant in Kyiv when he heard Trump on a cellphone call loudly asking Sondland if the president of Ukraine had agreed to carry out a probe on former Vice President Joe Biden. Sondland apparently told Trump that Ukraine’s President Volodymyr Zelensky “loves your ass” and would do anything he asked.

“I then heard President Trump ask, ‘So, he’s gonna do the investigation?’ Ambassador Sondland replied that ‘he’s gonna do it,’ adding that President Zelensky will do ‘anything you ask him to,’” Holmes told lawmakers, according to a copy of Holmes’ opening statement that was posted by CNN.

When the call ended, Holmes said he asked Sondland whether it was true that Trump didn’t really care about Ukraine. Sondland replied the president was only interested in “big stuff.” “I noted that there was ‘big stuff’ going on in Ukraine, like a war with Russia,” Holmes went on, “and Ambassador Sondland replied that he meant ‘big stuff’ that benefits the president, like the ‘Biden investigation’ that Mr. Giuliani was pushing.”

That testimony is key for several reasons. First, it undermines the defense by the White House that Trump didn’t really know what was going on. Plus it also raises even more questions about Sondland’s testimony, considering he had failed to mention to congressional investigators that he talked about Ukraine with Trump. And it also clearly throws a big question mark on Sondland’s earlier testimony that he had no idea Rudy Giuliani and Trump were interested in investigating a Ukrainian company because of its ties to Biden and his son, Hunter Biden. Holmes also confirmed again that there was some kind of quid pro quo, noting that Taylor told him in June that during a call with Zelensky “it was made clear that some action on a Burisma/Biden investigation was a precondition for an Oval Office meeting.”

Holmes said in his testimony that he only came to realize recently that he had information that could be of interest to the impeachment inquiry. “I came to realize I had firsthand knowledge regarding certain events on July 26 that had not otherwise been reported, and that those events potentially bore on the question of whether the president did, in fact, have knowledge that those officials were using the levers of our diplomatic power to induce the new Ukrainian president to announce the opening of a particular criminal investigation,” he testified.