Can anyone identify the original source of this statement? Or provide any other details?

The Pontchartrain's "... commander, Capt. John W. Dunnington mistakenly fired a few projectiles into a Texas cavalry encampment on the bank of the Arkansas river outside little Rock upon his arrival May 24. It was later learned the crew expected to find at least a part of Curtis' army at the city, ..."

I found this in an article in the DeWitt Era - Enterprise dated 1962

Thanks in advance for any help.