US President Donald Trump on Thursday night threatened to intervene in the Justice Department, saying the leaders of the DOJ and FBI “have to start doing their job and doing it right” because “people are angry.”

If they don’t do their job, he said at an Indiana campaign rally, he “will get involved and I’ll get in there if I have to.

His comments came after he told Bloomberg News in an interview that the Russia collusion investigation headed by Special Counsel Robert Mueller was “illegal.”

The president cited unnamed “great scholars” who say that “there never should have been a special counsel,” according to the news agency.

Some legal experts have questioned the Justice Department’s naming of Mueller, a former FBI director, to handle the probe in the absence of a specific law governing special prosecutors. But Trump’s own Justice Department says it is legal.