Expectations that the Democrat-controlled House of Representatives will impeach US President Donald Trump jumped late Wednesday morning, when special counsel Robert Mueller surprised the nation with a brief statement announcing his retirement and summing up his report on the investigation into Russian interference in the 2016 election.

Following his 10-minute address from the Justice Department, US stock indices fell to session lows amid speculation that his comments would prompt Democratic lawmakers to pursue impeachment. Both the Dow Jones Industrial Average and the S&P 500 reached lows not seen in months.

Mueller said nothing in his remarks that strayed from his team’s written report but stressed one point that seemed to completely contradict Attorney General William Barr’s characterization of the investigation.

Central to the special counsel’s decision making was a Justice Department guiding opinion that says no sitting president can be indicted for a crime. While Barr said in no uncertain terms that the policy had nothing to do with the decision not to pursue obstruction of justice charges, Mueller highlighted that issue as central to the outcome of the investigation.

“If we had had confidence that the president clearly did not commit a crime we would have said so,” Mueller said. But, he added, in light of the Justice Department opinion, “charging the president with a crime was, therefore, not an option we could consider.”

Further stoking talk of impeachment, Mueller explicitly said that “the Constitution requires a process other than the criminal justice system to formally accuse a sitting president of wrongdoing.”

There is a consensus opinion among political analysts that an impeachment proceeding in the House, which would be only symbolic as there is no support in the Senate for removing the president, would actually help Trump politically.

But the uncertainty appeared to add to the myriad reasons for anxiety on Wall Street, with some analysts even speculating that China would see this as a reason to continue a hard line with a weakened president.