Sept. 27 (UPI) -- Kurt Volker, the U.S. special envoy for Ukraine, resigned Tuesday, the same day multiple House committees scheduled to depose him on President Donald Trump's phone call with Ukrainian President Volodymyr Zelensky.
The student newspaper at Arizona State University, The State Press, was the first to report Volker's departure citing a school official. Volker is the executive director of the McCain Institute, a Washington, D.C.-based think tank associated with ASU.
ASU President Michael Crow confirmed the news to The Arizona Republic.
On Friday, the chairmen of the House committees on foreign affairs, oversight and reform, and intelligence, sent a letter to Secretary of State Mike Pompeo informing him they scheduled a deposition of Volker for Thursday. The deposition is related to the committees' investigation into reports Trump pressed Ukraine to investigate former Vice President Joe Biden and his son, Hunter Biden.
The committee chairmen accused Trump of jeopardizing national security by withholding tens of millions in military aid to Ukraine.
Volker's resignation comes days after the White House released a memo of a phone call Trump had with Zelensky in which the president urged Ukraine to investigate the Bidens. Scrutiny over the phone call began last week when a whistle-blower in the intelligence community filed a complaint with the office of the director of national intelligence over the July call.
Trump and his personal lawyer, Rudy Giuliani, have both said they have encouraged Ukraine -- in other conversations -- to carry out an investigation into Joe Biden and his son, Hunter Biden. Trump accused the Democratic presidential candidate of pressuring Ukraine to fire Prosecutor General Viktor Shokin, who was investigating Burisma, a gas company for which Hunter Biden served on the board.
Shokin's successor, Prosecutor General Yuriy Lutsenko told Bloomberg in May that the investigation into the company began before Hunter Biden joined the board, and he wasn't specifically a target of the probe. Additionally, Bloomberg reported the investigation into Burisma ended more than a year before Joe Biden called for the ouster of Shokin.
Multiple Western countries, including the United States, had called for Shokin's removal due to allegations of corruption.
On Thursday, Giuliani told Fox News that Volker asked him to speak to officials in Ukraine about the Bidens. Giuliani shared text messages he said he received from Volker about the issue. He said the messages were proof he only contacted Ukrainian officials as directed by the State Department
"As discussed, connecting you here with Andrey Yermak, who is very close to President Zelensky. I suggest we schedule a call together on Monday -- maybe 10am or 11am Washington time?," one message allegedly read.
The House intelligence committee released a whistle-blower complaint Thursday that provided details from the phone call and other instances in which Trump used "the power of his office to solicit interference from a foreign country." The whistle-blower also accused the administration of attempting to "lock down" the record of the July phone call.
ASU didn't comment on Volker's future with the McCain Institute.