Deleting Account Issues

My macbook pro was just given to me and in the process of deleting the former user (who had 200gb of stuff on the MacBook) through secure delete finder froze. I asked for help and the person who helped forced the computer off and on by holding down the power button. The user account is gone.... But there is still 200gb of memory space being used up. I tried going to the /users folder but there is nothing there and /users/deleted users does not exist.

Can anyone give me some help in deleting these files?