Duke was the first school to offer Williamson, a 6-foot-2, 210-pound athlete.
"[The UNC offer] means a lot," Williamson said. "Ever since I was little, I was a Carolina fan. For them to offer me, it makes me happy."
UNC is recruiting Williamson as a linebacker, even though he has primarily played safety for Durham (N.C.) Jordan.
"In Jordan's defense, I am basically an outside linebacker, because I'm in the box a lot," Williamson said. "So playing [linebacker] in college won't be any different. I love defense and I love to hit."
After finding out about the offer from his father on Monday, Williamson contacted the UNC football office."
"They just said I had a good attitude, personality, and the athleticism is there," Williamson said.
Williamson also placed a call to former teammate and current Tar Heel T.J. Thorpe.
"I was asking him what made him commit early [and] what made him want to go to Carolina," Williamson said. "He just told me the family atmosphere, it's fun, [and] you can have a great college career. And they sent nine people to the NFL so that's telling me they know what they're doing in trying to take you to the next level."
Thorpe being on roster can only help UNC's chances.
"I'm glad, because I'll know somebody there," Williamson said. "He'd tell me what to do and how to do it, if I were to go to Carolina."
For much of his recruitment, Duke has been Williamson's leader. Recently, though, those feelings have changed.
"Duke and I haven't talked like we use to," Williamson said. "I call and they don't pick up. So we haven't been talking as much. I've talked to the coach every once in a while, but ever since Carolina started really recruiting me [Duke] hasn't been showing me as much interest."
Now, Williamson claims a top four of Clemson, Duke, Georgia, and UNC.
"I'd say Carolina, Georgia, and Clemson are at the same spot, because of the interest they are showing me," Williamson said.
Williamson, who will return to Duke on Sunday for the Nike Camp, is unsure when he'll make a verbal commitment."
"Whenever I feel comfortable with making that commitment, I guess I'll do it," Williamson said.
Over the summer, Williamson plans to camp at Clemson, Duke, and UNC.
Video provided by Jason Pughe of AthleteVault.com.