Safe behind painting at rebel mission

[cane]

Anyone has any clue on this one?

On the mission where i should execute alvaro sosa and find the evidence to tanya tormens there should be some evidence behind the painting in a safe at sosa´s office but i cannot find that painting.
How to get that evidence?

[Jules]

Alot of the original 7.62 fans have alot of these tips and info here;
http://www.strategyfirst.com/forum/showthread.php?t=35010