How to make peace with insecure coworker?
I've worked at my current job about a year, engineering job working on a quoting system. My coworker Jonathan has been positive, energetic, and very gung-ho about our project and working with him was great for a long while. He does talk a lot during meetings and tries to steer most discussions, which makes meetings drag on longer than needed, but that has been fine.
A few months ago he sent me a private message giving me a "professional courtesy" that I should speak less during meetings and try to be more team-oriented and not climb over my colleagues to get promotions. This caught me totally by surprise, because I have always been mindful and open when working with others. I called him and we talked for about an hour about it. I guess he had coworkers in the past who took credit for his work and he's pretty sensitive to that, but after listening to him and explaining my motivations for how I work, he totally changed his message. He actually said that nothing was wrong, to disregard what he said, and he said he was grateful to have someone like me on the team. It seemed to me like he just needed to feel listened to and understood.
Then things were fine for a few months, until I worked on a task that he had wanted to work on. It was 30 minutes, very simple, and it didn't occur to me that he would want to be the one to do it. He gave me another private "professional courtesy" message not to "take action items from team members" and that he didn't need someone "doing his work for him" or thinking that he "wasn't capable" of it.
I apologized and tried to call him to understand his expectations better, but he refused to have another conversation like the first one. It's been a few weeks now and he's been acting out in frustrating ways. He pushes back on my work now, is intentionally vague and difficult when I have to get information from him, and acts condescending when I try to have discussions with him.
My other coworkers have noticed and have asked me if something is going on, so I know it's not just me.
I was asking for more details on a task he gave me, and when he was being difficult, I messaged him saying he was being more abrasive than was necessary and he said it was because I was "asking questions about things that had already been approved", as if that would even be a valid reason to be rude and aggressive.
I don't know, the vibe is totally different now and it's making me dread going in to work. I feel like I have done everything I can to repair the relationship, but it seems like he is insecure and has decided to target me and sacrifice a year of relationship over a 30 minute task that he interpreted as an attack or something. I think he's intimidated or jealous of me and I don't know how to handle that.
It's at the point that I'm probably going to bring it up to my supervisor soon, but is there anything else I can try to get back to at least a working relationship? Once it becomes a workplace issue or he gets disciplined, I don't think there's any salvaging the relationship.