Open Question: My boyfriend sleepwalks and is at times violent...?

My boyfriend and I live together and there have been several incidences where my boyfriend has been sleepwalking and has covered my face with a pillow saying "I'll fucking kill you!" and has punched me in his sleep while yelling "I'll beat the shit out of you!"... It's happened a total of five times now, I know this because it's scared the crap out of me each time. I know that when he was