Co-workers can be really hard to deal with, and there's always at least one a-hole. If that one goes away, someone will either turn into one, or another will get hired. There is ALWAYS at least one a-hole.
It's something you should expect at any job you get. Some are petty and mean, some are tattle-tales, and some are thieves and liars. Knowing this in advance can help you deal with it.