Carolina's dream run came to a close on Sunday, however, as the Patriots (25-7) absorbed a 16-2 opening run by the Tar Heels.
But with GMU packed tight in a zone defense, the Tar Heels suffered through a field goal drought lasting nearly five minutes which enabled the Patriots to get within five before a Hansbrough stick back dunk made it 23-16 with 3:59 to go before intermission.
Back-to-back dunks by Tyler Hansbrough and David Noel helped Carolina go to the locker room ahead 27-20 at the break. Still, in a defensive battle much like the opening period versus Murray State on Friday, UNC shot just 34 percent from the floor while holding the Patriots to 29 percent in the first half.
The 27 points was the Tar Heels' lowest scoring output in a half this season.
George Mason scored eight straight points to start the second half, aided by its trapping defense which forced UNC into six turnovers in its first seven possessions -- and the Patriots led for the first time 28-27 with 17:48 remaining. When Williams then called a timeout, Patriots' players along with their coach Jim Larranaga were pumping fists to the crowd.
Finally, a three by Terry stopped the bleeding momentarily, but a driving layup by Lamar Butler with the shot clock winding down tied the score at 30 apiece.
UNC battled back to tie it 54-54 when Noel hit a three from the corner with 3:01 remaining. But for some reason the clock operator waited to change the score. It was then during a timeout, Williams made what he called his biggest mistake of the game – calling for a full court press on the Patriots' ensuing possession.
"We called a timeout, and I looked up to the clock and it still said 54-51," Williams said. "In my mind, I thought something was wrong. I called a press and we didn't do a very good job on the press. It was a bad call on my part. It's something as a coach that you hate to do to hurt your team."
Butler got free down court and was fouled by Noel, who vehemently claimed he had gotten all ball. Butler nailed both free throws and the Tar Heels never got any closer. Threes by Wes Miller and Bobby Frasor with less than 35 seconds left made it interesting, but Butler, Folarin Campbell and Tony Skinn hit 9-of-12 free throws down the stretch to preserve the win.
"They came out and executed in the second half," Noel said. "They got us to turn the ball over and went on a great run.
"We just relied on our jumper too much, we didn't get inside to Tyler like we normally have. When you're shooting that many three-pointers, you're not getting to the foul line that much. So I think we shot ourselves in the foot in that aspect."
Playing in his final collegiate game, Noel scored a game-high 22 points.
"I think David Noel epitomizes what we want all student-athletes to be," Williams said. "I'm better today because I have coached him."
Hansbrough added 10, but was held to just one field goal in the second half.
"They sent a lot of guys at me," Hansbrough said. "That was part of their plan, send a lot of double-teams. They were pretty aggressive. It was frustrating."
The Patriots were led by Butler and Campbell, who scored 18 and 15, respectively.
George Mason advances to the Sweet 16 for the first time in school history, and represents the first Colonial Athletic Association since Richmond accomplished the feat in 1988.