House Judiciary Committee Chairman Jerry Nadler said Friday he sees "considerable evidence of obstruction of justice" in special counsel Robert Mueller's report, but isn't sure where congressional investigations will end up. Nadler issued a subpoena for the full, unredacted report and its underlying documents to the Justice Department Friday morning.

"I see considerable evidence of obstruction of justice, which is what Mueller said," the top Democrat told "CBS This Morning" the day after the release of Mueller's report.

Attorney General William Barr has already been invited to testify before Nadler's committee and Nadler said he will likely extend an invitation for Mueller to testify before his committee. Mueller has given the Justice Department a May 1 deadline for turning over all Mueller documents.

Despite the president's insistence that Mueller's report vindicates him, Nadler called the report "very damning," as it "paints a picture of a president who lies all the time," and demands others to lie for him, the top Democrat said.

Nadler had strong words of disapproval for Barr, who appeared to defend the president in a news conference ahead of the report's release. Barr explained to reporters in a prepared statement that Mr. Trump was frustrated with an investigation he viewed as illegitimate.

Nadler told "CBS This Morning" Barr has been "acting as the president's personal attorney," rather than as the top law enforcement official beholden to the U.S. Constitution.

Still, Nadler was cautious — as other top Democrats like House Leader Steny Hoyer have been in the last 24 hours — on the topic of impeachment. Nadler said he's cautious about the possibility of impeachment because, in his mind, moving forward with impeachment proceedings requires three things — belief that one can prove impeachable offenses; believe that those impeachable offenses are serious; and a belief that evidence for impeachment is so strong before any proceedings begin that even many of the president's supporters would agree.

So, what's the end goal? Nadler said that isn't clear, but insists Congress must see the full report, including underlying documents and redacted text.

"I don't know where we're headed," Nadler said.