A Marine Corps sergeant is going public with new charges of abuse at the Guantanamo Bay detention center. The sergeant visited the base in late September and tells ABC News she was "shocked" to hear several guards from different parts of the camp speak openly of mistreating prisoners. One said, "I took the detainee by the head and smashed his head into the cell door," she tells ABC News. Another "was telling his buddy, ‘Yeah, this one detainee, you know, really pissed me off, irritated me. So I just, you know, punched him in the face.’" See the full report on what she says she heard and saw at Guantanamo Bay — and what the Pentagon is doing about it — tonight on World News with Charles Gibson.