I would recommend sending him calming & positive thoughts.
You can also try using crystal & cleansing, shielding & grounding your personal energy.
Sorry to hear you have this negative person at your job. I had to share my office with a lady that has a huge cloud of negative energy around her. It was terrible, so drained me. I put on my desk small containers of sea salt and black salt, and one with some crystals ( quartz and amber and rose quartz). Acting busy was good for avoiding conversation. What also helped was telling myself, you are there, and I am here, with a wall between. Current status, she transferred to another office.