Well, it started when our boss basically turned him into a supervisor. When he was a fellow co-worker, he didn't display power-tripping at all. No arrogance was there. However, nowadays, the way I see it, it's randomly, I don't think anything specifically from fellow co-workers triggers his power-tripping. What I think triggers it is when he is fed massive
(from our boss) that he overdoes himself and pours it out on everyone.
I don't think it's about errors that are most likely he's going to point out, it's more like there's "always an error" someone makes, small or big. For instance, if you're 5 minutes late, he'll point out despite him being over an hour late. If you made a water spill that someone made, he'll point it out, despite him making the exact spills. My guess is that he does this to make himself "better" to the boss, and ironically enough, our boss sees right through this. In our own boss's words "He blames everybody, but himself." You could do the perfect job, but "you forgot to flush the toilet" to a co-worker.