The Departed: help me with a few loose ends. Spoilers

[hyde]

really great movie.

1. Did the plot line ever indicate that the shrink opened the envelope DiCaprio gave her? Question 3?

2. Towards the end Matt Damon is in his building with groceries and a woman with a dog avoids him disdainfully and pulls the dog away as he tries to pat it. Why?

3. And immediately after that he gets shot. Is the shooter yet another informer or just a vigilante?

ty