This may be a simple matter, such as anger over the state of the office, or it can be more personal. There are some valuable skills in managing a person's anxiety, and to reduce the probability of conflict. Personal space is the area around a person that others are not expected to intrude. Invading people's space can be a violation. It can make people feel attacked, mocked, pressured.
People become uncomfortable or defensive.
Violating personal space aggravates anxiety. Eye contact is another way in which people can express a range of feelings. A direct stare can be downright confrontational. Eye contact is often used in a passive aggressive manner, such as refusing to look at someone. Squinting may display judgement, and so on.