Unfortunately, what's done is done and he must pay if the IRS says he owes. Be sure to explore all options using turbotax as you might be able to use credits and deductions to lower his gross income to a point where his liability is zero - it all depends on how much gross income he actually made. As others have mentioned about 14K is where you start giving your hard-earned money away to the government to mis-spend lol.
The employer is not obligated to do any witholding AT ALL if you submit a W-4 that says you are not subject to witholding (ie you state you are exempt from witholding). It's been a while since I have filled out a W-4 but you used to be able to just state a number for roughly how much the would take out - the lower the number the more that would be withheld out of your paycheck. But looking at the form now... I don't see where you put a simple integer number anywhere and there is some obnoxious table with salaries on the top and bottom (!) and you are supposed to enter some actual dollar amount. Good luck figuring it out - I'm trying to understand what mess they made of the W-4 since I last filled one out lol.
