Dream of a mouse - what does it mean?

I dreamt that I was in a factory and that I saw a mouse. People around me were planning to kill it, so I decided to chase it, to save its life. I ran around chasing it up and down stairs until finally I caught it by the tail. I then carried it outside as it struggled and placed it on the front step. As I set it down, I went to close the door, as I did, he tried to run back in, but I ended up beheading him with the door. His body began to convulse despite his lack-of-head. I remember I felt remorse for this. I don't know what this dream means though... any ideas?