The Orcs of the Sutcrofts have too long been encroaching ever-closer to Snowbourn. Fastred's fervour is not misplaced, though a bit extreme - the less Orcs the Rohirrim have to contend with, the better.
You have encountered an Orc of the Sutcrofts. Fastred would be greatly pleased if more of their kind were purged from the Sutcrofts.
Fastred has decreed that no Orc is to find shelter in the Sutcrofts and all must be slain.
Orcs can be found throughout the Sutcrofts, especially near Snowbourn.