In a painting entitled "Crucifixion of the Parlement of Paris" (1452; artist unknown) it appears that someone is trying to garner attention away from the crucifixion.

It is quite jolting when your eyes suddenly hit this unexpected horror.

There appears to be a character to the right of the cross who has been beheaded and is holding his own head in his hands.

Whatever could be the meaning of this?

The beheaded man is St. Denis, the patron saint of Paris.