|"Soldiers' remains unburied on the battle-field of Bull Run" by Andrew J. Russell|
(Source: Colgate Library)
The main soldier-correspondent for the Lancaster Daily Evening Express in the Pennsylvania Reserves was a private in Capt. Easton battery of Pennsylvania Reserves artillery named George McElroy. His letter dated April 16, 1862, describes a walk over the battlefield and the appalling sights he took in. The horror he expressed fits in with a pattern of indignation McElroy directed towards Southerners in early 1862 for various reasons such as the vandalized state of one of the Washington family graves (I think Martha Washington at Mount Vernon, but I might be wrong) and especially the lightened skin tones of slaves.
From the April 19, 1862, Daily Evening Express: (alternate link)