He knows he did a bad thing and did not have a clean conscience after that. In the shots I did he looks at the taco restaurant's logo and one of the tacos, that represented his brother would talk to him as if it was his conscience saying he did a bad thing to his brother.
I thought it was a great idea and it could have been fun to see it in the final film but they decided it was not and dropped them from the final version.
The other day I saw a scene from the Sopranos where a fish in a farmer's market talks to the character of Tony Soprano as if it was his conscience playing with him.
So, there you go.
taco 1 from Sandro Cleuzo on Vimeo.
taco 2 from Sandro Cleuzo on Vimeo.