R.C. Smedley, History of the Underground Railroad in Chester and the Neighboring Counties of Pennsylvania (Lancaster, PA: John A Hiestand, 1883), 107-108.
There was a band of "Land Pirates" known under the familiar name of the "Gap Gang," scattered throughout a section of that country, who frequently gave descriptions of these colored people to southerners which led to their capture; and when opportunity offered, they assisted in kidnapping free negroes, and carrying them into the Border States to be sold. This exasperated the colored people against all slave-hunters, and they held meetings, assisted by their white friends, to consider and adopt means for self-protection. The man who stood prominent among their race in that vicinity as one of acknowledged intelligence and indomitable will, was William Parker. He possessed a strong social nature, and would at any time put his own body in danger to protect a friend. These qualities gained for him the respect of a very large class in that community for:
And noble souls in nature are allied."
He had repeatedly foiled the kidnappers in their undertakings, rushed upon them in defiance of their weapons, beaten and driven them before him out of the neighborhood, as one man may put a herd of buffaloes to flight. He was therefore the one above all others whom they wished to get rid of.