In the books, Perrin killed two Whitecloaks in a fit of rage, thus explaining his aversion to violence afterwards and why the Whitecloaks were after him and Egwene.
Eamon Valda is not in the first book and comes around later in the series. He is an Inquisitor, an especially devout and sadistic unit of the Children of the Light who job is to attain confessions of guilt through torture. The Children of the Light are an extremely militant group with Inquisitors having no rank and therefore no authority to order other men. However, the threat they represent and their special access to the Lord Commander makes most officers reluctant to get on their bad side.