Here's a much better idea: -
Take the FO's license from him/her, shred it, and make them think very closely about what the hell they were doing with a firearm on FINAL APPROACH - or even having it out its container in an unsafe state for god's sake before being allowed anywhere near the pointy end again.
It's incidents like this that clearly illustrate firearms in the flight deck are dangerous, and have no place in a locked container or shoulder holster of the Wyatt Earp wannabes of US aviation.