Dream of person, chased, girlfriend

My girlfriend , a couple of people and I were all in a house with some sort of crazy person following us. He chased us and my girlfriend and the two other people hid in one room and me another across the hall. Then the crazy person threw some sort of explosive in her room then in my room. I was able to escape unscathed but my girlfriend did not. She lost her right arm as we all ran outside. She was crying as I carried her while we were being chased.