I don't think the Carver is anyone they know. The Carver first attacked outside their circle. I wanna say McNamara heard about it on the news or something, but I forget. He initiated contact with the victim. So the chances that it was someone they knew ahead of time would be ridiculously remote. How could anyone predict McNamara would initiate that contact? So you'd have to conclude it's just some psycho. If they know the Carver, it's because the Carver initiated a relationship with them AFTER the first attack and surgery. Hey... maybe it's the British cop!!!
But I could be remembering wrong. Did anyone refer them to the first victim?
Funny note... the actress who played the Carver's first victim - Leslie Bibb - was a hall-mate of my wife their first year in college.