Need some answers (spoilers)

Rating: 7/10 (9 October 2006)

1. Who actually was Costello (what exactly was his involvement with the FBI)? 2. Who all were the moles on each side (Wahlberg wasn't dirty was he)? 3. Did Wahlberg do what he did at the very end for justice? How did he know that Damon was dirty? I think I have answers to these questions, but I would appreciate it they could be cleared up for me. thanks in advance As for the movie, I liked it up until the elevator scene. I thought it was a little over the top. The other mole that Damon shoots just seemed to be insignificant and gave stupid reason as to while he was helping Damon. Also, I am all for realism, but there were so many graphic shooting deaths that it started to get comical after a while. thoughts??