Rob Kardashian's shocking Instagram post about his big sister, Kim Kardashian, was finally explained.

Last week Rob compared his sister Kim to a bloody screenshot of Amy Dunne (Rosamund Pike) from "Gone Girl."

 This is my sister kim , the bitch from Gone Girl,,,

A photo posted by ROBERT KARDASHIAN (@robkardashian) on Mar 22, 2015 at 10:38am PDT

The post remains up, but he hasn't posted anything since.

Apparently the post was Rob's way of calling Kim out for being two-faced, reported Us Weekly.

"Rob is in a dark place," an insider reportedly told Us. "Kim told him he needs to get out of his funk."

A second inside source confirmed this comment to Us, saying, "His post was about how she seems caring in public, but he feels ignored."