There's a lot of rage that can come with depression. If I can't control my own happiness, it makes me feel weak. I personally, get pissed when I can't control my own though process. I mean, even if I can't control anything in the world around me, I should be able to control myself. I always feel like my depression is ridiculous and I should just get passed it, but I can't. It is that very complex that turns me into a jerk. I have to fight it like hell and remind myself that people around me don't know what's happening in my head and it's not their fault I'm this way. It's hard. I'm always pissed, even if it's below the surface, I'm always angry. It never leaves. I just find ways to let that anger out that wont' hurt anyone. I'm not perfect about it. I say some pretty nasty things to the people who are the closest to me.
When an animal is hurt and backed into a corner, it's not going to let anything come close to it and can have the deluded perception that everyone's the enemy.
I don't know if this is exactly what you're feeling but know that it's normal and you have to work at it all of the time to keep from becoming one of those jerks.