In a shock move, the US Justice Department appointed a special prosecutor to oversee an investigation into possible collusion between Donald Trump's presidential campaign and Russian officials. 

This decision was apparently made by Deputy Attorney General Rod Rosenstein, who had reportedly been put out that the Trump administration tried to make him the fall guy for the ouster of FBI director James Comey.  His boss Attorney General Jeff Sessions had recused himself from matters involving the Russian probe, although Sessions is apparently helping to interview candidates to replace Comey.

"In my capacity as acting attorney general I determined that it is in the public interest for me to exercise my authority and appoint a special counsel to assume responsibility for this matter," Rosenstein said in a statement.  "My decision is not a finding that crimes have been committed or that any prosecution is warranted.  I have made no such determination.  What I have determined is that based upon the unique circumstances the public interest requires me to place this investigation under the authority of a person who exercises a degree of independence from the normal chain of command."

Rosenstein picked Robert S. Mueller III - a widely-respected former prosecutor who served as the FBI director from 2001 to 2013 under Presidents Bush and Obama.  Mueller's appointment was hailed by Democrats and Republicans alike, as well as those in the national-security community.  "I accept this responsibility and will discharge it to the best of my ability," Mueller said in a characteristically terse statement.

Up until his appointment, Mueller was a member of the law firm that represents Ivanka Trump and her husband Jared Kushner.  He immediately resigned when he accepted the Special Prosecutor's role.  A senior partner in the firm says Mueller's work didn't involve any members of the Trump family or their businesses.

Mueller and Comey both rose to national prominence in 2004 when they threatened to resign from the Bush Administration over administration attempts to conduct warrantless wiretaps.  At the time, Mueller was FBI director and Comey was the deputy attorney general.  The White House eventually backed off, and both established reputations for independence.