After the Civil War a vigilance committe known as "The Reign of Terror" operated in Johnston County, Missouri.  Between February and August of 1865 they were responsible for the murders of more than a dozen men.  This company of vigilantes is notable because, immediately after the war, it included both Union and Confederate veterans, church leaders from both the Southern Baptist and Northern Episcopal churches, teachers, a librarian, and a bevy of civil leaders.  One of the men credited with co-founding the committee was F.M. Cockrell, a former Confederate general who would rise to political prominence during the tenure of Teddy Roosevelt.

Go here to read about the Reign of Terror at The University of Missouri's Online Library.  This account was written within living memory of the events portrayed.  It begins on the page that will come up on the pageviewer.  Use the drop box on the right above the viewer to go through the rest of the story.

Here is Cockrell's biography at the official site of the U.S. Senate.  Oddly, it doesn't mention his credentials as a vigilante.