Democratic frontrunner Joe Biden walked out of a press conference without taking questions about his son's business dealings in Ukraine because he "doesn't have the answers," a CBS News contributor said Tuesday.

"He walked out before taking any questions," Molly Hooper, a Capitol Hill reporter for the Hill, told CBS News on Tuesday. "He doesn't have the answers yet to a lot of these press questions, and he doesn't want it to be unscripted."

CBS News host Reena Ninan began a segment on the press conference by asking Hooper what she thought of Biden's comments. Hooper laughed as she told Ninan about Biden walking out.

CBS News political correspondent Ed O'Keefe was visibly annoyed by Biden's press conference, saying it is "unclear" why Biden "decided to summon" reporters to "downtown Delaware." Biden failed to clarify "what exactly he or his son had done in Ukraine," O'Keefe said.

During the press conference in Wilmington, Del., Biden said he supports impeaching Donald Trump if the president does not cooperate with Congress. Biden's press conference, which concluded with the former vice president not answering any questions and walking offstage, followed news that Speaker Nancy Pelosi (D., Calif.) would announce a formal impeachment inquiry.

"Using its full constitutional authority, Congress, in my view, should demand the information it has a legal right to receive. If a president does not comply with such a request to Congress, if he continues to obstruct Congress and flout the law, Donald Trump will leave the Congress with no choice but to initiate impeachment. That would be a tragedy, but a tragedy of his own making," Biden told reporters. "We know who Donald Trump is, it's time to let the world know who we are."

Biden added he could take "political attacks" from Trump, but would not let him "get away with shredding the United States Constitution."

Democratic lawmakers have renewed their push to impeach Trump amid a whistleblower complaint related to a conversation between Trump and Ukrainian president Volodymyr Zelensky. The conversation over a July phone call was about Hunter Biden's lucrative dealings a Ukrainian natural gas company. Trump has repeatedly said he didn't pressure Zelensky to investigate Hunter Biden. He released notes taken of the call on Wednesday.