Shooting game

Hi, I havent used flash in years and I wanted to make a game. Ive made a few before but i didnt ever finish them and now i dont have them anymore.

I wanna make this game where you are this man that can move around. (i can remember how to do that) and you shoot these huge exploding cats.

How do i make the person shoot when you press the spacebar?
How do i make the barrel of the gun follow the mouse and the bullets shoot that way?

Thanks