to know what had happened - they were very disorientated. The body of the driver was put into a body bag. One medic handed over the dog tags belonging to the dead soldier to another medic and, at this point, Sergeant Ken Kozakiewicz realised that his best friend had been killed by "friendly fire".

The World Press Photofoundation celebrates the 50th anniversary of its annual photographic competition this year.

In the first of five pieces by photographers talking about their award-winning work, David Turnley describes how he captured the image of a young US sergeant at the moment he learns that the body bag next to him contains the body of his friend, killed by "friendly fire".

The widely published photo became an iconic image of the 1991 Gulf war -a war in which media access was limited by Pentagon restrictions.

Here are some more award winning photographs from over the years.

1963:While working for the Associated Press, photographer Malcolm Browne was in Saigon, South Vietnam, when Thich Quang Duc dramatically protested against alleged religious persecution by the government. Browne was overcome at the horror and smell of burning flesh.

1973: Many of the winners are controversial, as is this one, which shows the president of Chile, Salvador Allende, moments before his death during a military coup. The picture was sourced by Marvine Howe working for The New York Times, the photographer is unknown.

1964: Don McCullin was covering the conflict in Cyprus for The Observer newspaper when he took this picture of a Turkish woman who has discovered her husband’s body.

1976: