Well you should document his behavior either write it down or even record it using your cell phone, you can Evan just use the voice recorder on there most phones have them. Speak with your supervisor, tell them that you have fear of the guy and you don’t want to be slammed by the keyboard on his next ranting episode. Explain to your supervisor how also your progress is lacking due to his behavior and that is not the employee you want to be. Next find ways to focus on the work you do and not let him be a distraction, you have to tune him out. I had to do this a few times with coworkers in the past , otherwise I focused in on the negative of the behavior that it was preventing me to do my work. When you focus on the badside of people that’s all you will see in them .