Since 2012, the Ukrainian prosecutor general had been investigating oligarch Mykola Zlochevsky, owner of the oil and natural gas company Burisma Holdings, over allegations of money laundering, tax evasion, and corruption.[20] In 2014, then-U.S. Vice President Joe Biden's son, Hunter Biden, joined the board of directors of Burisma Holdings.[21] In 2015, Shokin became the prosecutor general, inheriting the investigation. The Obama administration and other governments and non-governmental organizations soon became concerned that Shokin was not adequately pursuing corruption in Ukraine, was protecting the political elite, and was regarded as "an obstacle to anti-corruption efforts".[22] Among other issues, he was slow-walking the investigation into Zlochevsky and Burisma * to the extent that Obama officials were considering launching their own criminal investigation into the company for possible money laundering.[20]
In March 2016, Joe Biden threatened Ukrainian President Petro Poroshenko that if he did not fire Shokin, that the US would hold back its $1 billion in loan guarantees. "I looked at them and said, 'I'm leaving in six hours. If the prosecutor is not fired, you're not getting the money.' [...] He got fired. And they put in place someone who was solid at the time."[23] Shokin was dismissed by Parliament later that month.
Shokin claimed in May 2019 that he had been investigating Burisma Holdings.[24][25][26][27] However, Vitaliy Kasko, who had been Shokin's deputy overseeing international cooperation before resigning in February 2016 citing corruption in the office, provided documents to Bloomberg News indicating that under Shokin, the investigation into Burisma had been dormant.[28] Hunter Biden's ties to Burisma Holdings was criticized as a conflict of interest in a New York Times editorial, though Amos Hochstein has claimed to have never seen coordination between Joe Biden and his son on the matter.[29][26]