In "To Kill a Mockingbird," when Mr Ewell arrived on the scene,what did he see through the window that infuriated him?

In Harper Lee’s To Kill a
Mockingbird, Tom Robinson, a black man wrongly accused of raping Mayella
Ewell (a white woman), announced while on trial that he felt sorry for Mayella.  He knew
that she was often alone and wished for some company.  So, one day on his way home, she
asked him to help her with something inside the house.  Although he was weary of such a
favor, his compassion for her was too strong.  He agreed to help, but when he got inside
the house she began to hug and kiss him.  Being frightened of this, Tom ran away, but
the damage had already been done.  Bob Ewell had seen everything from the window and in
a rage; he violently beat his daughter to punish her for berating herself to the point
of throwing herself in a black man’s arms.  Of course, not wanting to admit to the
violence himself, Bob accused Tom of raping his daughter.