The Missouri in the Civil War Message Board

Union Court matrial records

I'm writing an article for the Watts Hays Letters website about Col. Upton Hays' involvement in the Border Wars and the Civil War. I have found and received several accounts of his death from members of this board. Apparently there was a Union army court martial and I would like to read the file. How do I obtain it? Does anybody know where the court martial took place? - MO, KS or AR I would guess. According to one Email I received the Capt. in charge of the Co. who shot Hays was a former business partner and another Email mentioned an Iowa unit.

From the Cornell U. Union CW records:
P636 HDQRS. Forth Missouri Brigade, Missouri State Militia
Pond Spring, September 15, 1862 (to Brig. Gen. Totten, Springfield)
- - They report that the officer shot by our pickets was Colonel Hays. I enclose a copy of a note from Colonel King in relation to it. - -E. B. Brown, Brigadier General
- (the note by King was not found)

Who was Col. King? I'm hoping his note will be in the court martial file.