In the state Provost Marshal's database, I found a petition in which the notorious Mr. Bowles is mentioned as taking part in an 1862 raid on the Bollinger County Court House. Here's the petition as I transcribed it. You can find the handwritten document itself on pages 1071-1073 of microfilm reel F1584 of the aforementioned database.

April 9, 1862

Petition

To his Excellency, H.W. Halleck, U.S.A
Major General Commanding Department of the Mississippi

We the undersigned Union citizens of Bollinger Co., Southeast Missouri, are and have been since the commencement of this war infested with several bands of rebel robbers and murderers, mounted upon the best horses in the country and said to be about seven hundred strong, under the command of four notorious rebels: Jason Hunter , Solomon Kitchens , Wm. Jeffers and a scoundrel named Bowles , all claiming to be in the service of the notorious Jeff Thompson , making midnight raids through this county in a circuit of 10 or 15 miles in and around the town of Dallas, hunting down Union men wherever they can find them, stealing their horses and work cattle, abusing their families and indiscriminately murdering every Union man that they can lay hand on. As an instance, on March 26, 1862, these scoundrels paid a visit to the neighborhood surrounding Dallas and took all the horses he had from a good Union citizen, Amos Baker, leaving him without the means to put in a crop thereby depriving his wife and family of support, stole horses from three other good union men Henry Crader, Maston Lyle and Joseph Miller and murdered the said Miller, shooting him three times and stabbing him twice after he was shot, [and] shot a soldier in the Missouri Volunteer Militia named Samuel Robbins, who came here on a furlough to see his sick wife. Proceeding to Dallas, they entered the courthouse and carried away all the books and papers in the county clerk’s office and took James Noel , clerk of the county court and member of the state convention, a prisoner to their camp. Since that time they have repeatedly stolen horses from other parts of the neighborhood and fired into parties of Missouri State Militia in or near the town of Jackson, and threaten[ed] they will shoot down any Union man who will attempt to make a crop. The town of Dallas is chiefly inhabited by returned rebels from Jeff Thompson’s camp, who have been to Cape Girardeau and taken the oath of allegiance to the United States but who are well known to act as spies, and harbor and encourage these murdering bands in their depredations.

Therefore, we your petitioners, relying solely upon your Excellency for protection, humbly pray you will send a force in this neighborhood and arrest and break up these bands of rebel robbers and murderers, and your petitioners will ever pray.

The petition was signed by more than 50 men, the first being John R. Cochran, who apparently hand-carried it to St. Louis. He subsequently became the commanding officer of three independent militia companies in Bollinger County.

I also have read somewhere in the papers of Col. Lindsay Murdoch, who was from Bollinger County, that he tried unsuccessfully to capture or kill "Bowles," although I am unable to provide a citation at this time. As in the petition above, no first name for Bowles was given in the Murdoch account.

I too came across the reference in the Official Records to the killing of "Dick Bowles" at the end of the war and assumed it was the Bowles mentioned in the petition. Now, after reading some of the comments in this string, I'm not so sure. Still it would be quite a coincidence to have two people named Bowles, or Boze, in Southeast Missouri who were both regarded as particularly noteworthy guerrillas.

George Williams