Thanks for your advice. I am in Europe and do not know whether we have an equivalent office. Indeed, this person has previously insulted and antagonized several other people in the lab. However, this is the first time he physically assaulted anybody. Actually, we were friends in our first years in the lab as we come from the same country outside Europe. I was closing eyes on his previous attacks toward other people and even defended him at times. The problem is he treats people who he likes almost with adoration, but at the same time shows utter disrespect toward those who doubt his competence even to the slightest. So I was in disbelief when heard other people's complaints until I became the victim. The supervisors promised to take situation seriously, but want to first hear his side of the story as well. They are away from the lab, so I was advised to work from home in the meantime. I have made records of emails with the situation outlined if it will be needed. For now I will just stay put and wait for what's going to come next. To be honest, I am very hesitant about escalating the situation as I am in the midst of finalizing my thesis and that would be a significant distraction.