Read the following excerpt from “The Cask of Amontillado” and answer the question. At the most remote end of the crypt there appeared another less spacious. Its walls had been lined with human remains, piled to the vault overhead, in the fashion of the great catacombs of Paris. Three sides of this interior crypt were still ornamented in this manner. From the fourth side the bones had been thrown down, and lay promiscuously upon the earth, forming at one point a mound of some size.

What is the meaning of the underlined word promiscuously as it is used in the passage?

impurely
immorally
haphazardly
systematically