As stated by Jaime Santa Cruz, it is taking a long time because it is saving his files to a disk image for backup. To stop that process, hold down the power button until you computer shuts off. You will be ok, but don't use this method for every issue you run into. It's fairly safe, but not foolproof.
A couple of assumptions here.....
- He must have had a lot of files.
- You probably don't want them
Here is the quick way to solve this issue (I am assuming you have Administrator rights to this Mac)
Using Finder, navigate to
/Users/
Inside that folder you will find a folder structure similar to the following:
Desktop
Downloads
Music
Pictures
You may have more folders than that. Go into each folder and delete everything by moving it to the trash. Delete all the folders, but leave that structure intact.
Next, remove the account as you did before. It should go very quickly now.
Now, I am not at my mac to confirm, but if I remember correctly, when you try to remove a user account it should present you with a few choices of what to do with the users home folder. If you don't want his data, you can choose to delete it.
What I described is basically the manual process of deleting the home folder so either method will work.