There had been some trouble in there earlier in the week. But, Mrs. Barnett is not a reliable witness since she was hit on the back of her head with the flat part of an axe. She reportedly was 'not right' since the attack that left her husband dead. Most of the people in this area are incredibly prejudiced as well.
Because RW and Melvin had black stockings over their faces so they looked black. Next time just read the book properly, no offence.