Just a couple plot questions... [spoilers]

[WindexGlow]

Why did the scientist that you gave the saw to try to kill you?
He was infected. I haven't played the game in a long time, but he sawed his arm off no?

What was the thing in the walls in The Kennels?
I think that was the human which turned into a dog, or something. There are notes in the area about him.

If Phillip and Red were infected, how come they didn't become zombies, like everyone else?
I think they were being used as pawns for the tuurngait. Red wanted to die, but the tuurngait would not let him (thus why Philip had to)