Army Sgt. Dwayne Cole was on his second tour of duty in Iraq and counting the days — 37 — until could return home. But everything changed that night when a bullet hit him in the neck: not by enemy fire, but at point-blank range by a member of his own unit. An accident? No, an army investigator said: A cover-up.

The shooting of a soldier in Iraq by a member of his own unit raises disturbing questions. (Dateline NBC)

Tom Wales, a federal prosecutor for 18 years, was murdered one month after the Sept. 11, 2001 attacks while in his home. The murder looked so much like a hit that investigators wondered, was the killer was someone Wales had put behind bars? If so, it would be the first time in U.S. history that a federal prosecutor was killed in connection with his work.

A Deadly Triangle: A student teacher is caught in an affair with one of her former students. And soon, the scandal becomes deadly: The student is shot- by the teacher's husband. Was it murder, or was it an accident? Read the transcript.

Billy Wolfe, an Arkansas high school sophomore, dreaded going to school each day. A regular punching bag for his classmates, all Billy wanted was someone on his side. But when even a videotape of kids bullying him doesn't convince his school he's a victim, Billy's family decides to sue.