action: I did three things to resolve the situation. First, I sought the advice of a teammate who had worked with him for much longer, to see if she could help me understand what happened. What she told me was that he was really insecure and tended to lash out. Second, I went back to him and took the responsibility on myself, saying that I screwed up in not keeping him informed of my work. I told him that I was new to this and didn't really know what I was doing, and asked him to advise me on how to manage it. This helped him feel better about himself, and also allowed us to work together to find a solution. Third, I pushed these changes out to the team since, really, it was a broader problem of how to keep two semi-independent projects in sync. I set up a process for weekly check-ins and goals, empowering individual people to ensure their completion.