Hunter Biden, the son of former Vice President Joe Biden, dropped a bomb on Wednesday when he revealed that he is under an official investigation for his “tax affairs” by federal prosecutors in Delaware.

“I learned yesterday for the first time that the U.S. Attorney’s Office in Delaware advised my legal counsel, also yesterday, that they are investigating my tax affairs,” Hunter said in a statement obtained by CNBC.  “I take this matter very seriously but I am confident that a professional and objective review of these matters will demonstrate that I handled my affairs legally and appropriately, including with the benefit of professional tax advisors.”

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Hunter did not reveal any other details about the investigation. A spokesman for David Weiss, the U.S. attorney for Delaware, refused to comment on the situation when contacted.

Joe Biden’s transition team released a brief statement on Wednesday, saying that, “President-elect Biden is deeply proud of his son, who has fought through difficult challenges, including the vicious personal attacks of recent months, only to emerge stronger.”

Hunter has been embroiled in various controversies over the years. During his father’s time as vice president under Barack Obama, Hunter joined the Naval Reserve only to be discharged after testing positive for cocaine in his system, according to the Associated Press. He later admitted to struggling with addiction for years, something his father addressed in a presidential debate earlier this year.

“My son like a lot of people at home had a drug problem,” Biden said, according to USA Today. “He’s fixed it. He’s worked on it. And I’m proud of him. I’m proud of my son.”

Another controversy that Hunter was embroiled in was him joining the board of Ukrainian energy company Burisma in 2014, which caused concerns over a potential conflict of interest considering his father was deeply involved in U.S. policy toward Ukraine at the time as vice president.

It remains to be seen where this new investigation of Hunter’s taxes will go.