How would you understand this expression?

It's from an English novel, the Good Soldier. The author is describing a scene in the past where something sad had happened. And the text goes:

"And it was dusk; the heavy, hewn, dark pillars that supported the gallery were like mourning presences; "

I'm not so sure as to what "mourning presences" means. I know it's a metaphor but does it mean the pillars look like a bunch of sad people？Like those who show up at a funeral? It seems so to me but not certainly.

Any input is welcomed. Thank you!