Tommy wasn't in the library, that was Nick, the DIK who lost his brother. He actually tells you a little about Vinny in the scene. I don't think it was Tommy, but the game do try to raise the possibility with him leaving the scene when Josy shows up.
The thing is that he seems to like the fraternity too much to do something like that, he doesn't have a good motive, for now, none of the DIKs do. The reason why i think we will join the DIKs next episode is that we need to know a little more about the other DIKs to better assess the situation, because aside from Rusty, Tommy, Jacob and Nick we don't know much about them.