I believe that abusers will abuse as long as they can get away with it. So that means they treat some people better (like coworkers) because the consequences of having their mask slip would outweigh the pleasure they get from the abuse. Online is an easy way to be abusive without having to deal with consequences, since he could just log off and that's it.

From experience, I'll tell you this: an abusive person will abuse you in any platform. I was abused online as well as in person. In fact, the abuse worsened in person to a level I could hardly even believe, it shocked me so much. And I was also told that it was my fault, that I "brought it out" in him, and he never acted like that with anyone else. It doesn't matter if he did or didn't, in the end it was all horrible (and of course abusers never stop at just one victim, if they can find another, they will).

Please don't blame yourself for what happened. It wasn't your fault.