CAIRO, Egypt — An extremist group posted a video on a Web site today showing a man being shot in the back of the head, and the group claimed the victim was American adviser Ronald Allen Schulz.

Meanwhile, a German woman released Sunday after being held hostage for three weeks is expected to leave Iraq soon, but she likely will not return to her homeland for some time, the German government said today.

The video purportedly posted by the Islamic Army of Iraq did not show the face of the victim, and it was impossible to identify him conclusively.

In a separate piece of film, shown on a split screen as the killing was aired, the extremist group showed a picture of the former U.S. Marine alive.

In an Internet posting last week, the group claimed it killed Schulz, 40, and then said later it would show the killing. The group said it had killed Schulz after the United States failed to respond to its demand for the release of Iraqi prisoners.