If you have to ask, it's usually best not to confront them directly. People who act this way are ready, even eager to get into a fight. Sort of like fighting a bigger person, you want to disarm them. A standard tactic is to be genuinely nice to them. You don't have to like them, but being polite makes them look worse when they are not. You can even be generous to them. This might actually give you some insight to why…
I've read an article that toxic coworkers actually do affect performance so I know this is hard.
But, in my experience, I wasn't exactly NICE but I was genuinely trying to be helpful, and sensitive to whatever the team needs. In the end, all I got was respect not only from him but from the team, which is the only thing I need.