I don't think so. There is no built-in support for that. You probably need a second computer.
While it is possible to start two instance of SG in window mode and resizing their windows to simulate a split screen, I assume, only one window can take the input of the mouse (and keyboard).
There is an ioquake3 fork called spearmint, which claims to have "Four player splitscreen support.". I did not test it, but this'd most likely require code changes to Smokin' Guns itself.