First off is the notebook 'frozen' completely (ie. he cannot even move the mouse etc.?) or is it just in a 'kernel panic' (ie. the spinning 'beachball')? 

If it is completely frozen he could try holding in the power button until the notebook turns itself off.  If it is not completely frozen he could try 'forcequit' on whatever application (likely safari if he was indeed browsing prior to the incident) and then a normal shutown.  I believe 'forcequit' is enabled/shown when you hold the OPTION and COMMAND keys and then left-click on the MAC icon and choose 'FORCEQUIT". 

Secondly, what OS and version of said OS is he running and/or what version make/model of the MacBook Pro series?

There may be some additional tips to provide but some may be OS and/or hardware specific.

Thanks Monk. It will have to wait until Tuesday because he just left. However, he did tell me that he was unable to shut it down. As for his OS I believe he has the one prior to the latest. His laptop is about a year old. I'll get the rest of the info next time I see him.

My Retina is like this, but it came with Mavericks. I know that it works like this as well...

Lion and Mountain Lion (if pre-installed on the computer at purchase*)

         Note: You will need an active Internet connection. I suggest using Ethernet if possible because

                   it is three times faster than wireless.

          1. Restart the computer while holding down the COMMAND and R keys until the Mac OS X

              Utilities window appears.

          2. Select Disk Utility from the Mac OS X Utilities window and click on the Continue button.

          3. After DU loads select your startup volume (usually Macintosh HD) from the left side list. Click

              on the Erase tab in the DU main window.

          4. Set the format type to Mac OS Extended (Journaled.) Optionally, click on the Security button

              and set the Zero Data option to one-pass.

          5. Click on the Erase button and wait until the process has completed.

          6. Quit DU and return to the Mac OS X Utilities window.

          7. Select Reinstall Lion/Mountain Lion and click on the Install button.

          8. Upon completion shutdown the computer.

Copied and pasted to notepad. Thanks phoon. As soon as I see him, probably Tuesday as he works on Mondays, I'll sit with him to make sure he does it up right.