A coroner ruled Friday that U.S. forces in Iraq unlawfully killed a British television journalist by shooting him in the head as he lay in the back of a makeshift ambulance during the opening days of the war.

The widow of reporter Terry Lloyd called for the perpetrators to be prosecuted for the "despicable, deliberate, vengeful act." And Deputy Coroner Andrew Walker said he would ask the attorney general to take steps to bring to justice those responsible for the death.

But prosecution of U.S. service members seemed unlikely.

The U.S. Defense Department said its forces had followed proper rules of engagement and that a U.S. inquiry into the killing of Lloyd, 50, a veteran reporter for the British television network ITN, "determined that U.S. forces followed the applicable rules of engagement."

"The Department of Defense has never deliberately targeted noncombatants, including journalists," the Pentagon said. "We have always gone to extreme measures to avoid civilian casualties and collateral damage."

Walker also said the inquest was unable to determine whether the bullets that killed Lloyd in southern Iraq on March 22, 2003, were fired by U.S. ground forces or helicopters.

Aidan White, the head of the International Federation of Journalists, the world's largest organization of journalists, said: "If this was murder, as the court suggests, and the U.S. is responsible, it is certainly a war crime."

The London-based National Union of Journalists welcomed the coroner's decision and also called the killing "nothing short of a war crime." Jeremy Dear, the group's general secretary, said: "The killing of journalists with impunity must never, ever go unpunished. Any attempt to silence journalists in this way must never succeed."

Witnesses testified during the inquest that Lloyd — who was driving toward the southern Iraqi city of Basra with fellow ITN reporters — was shot by Iraqi troops who overtook his car, then died after U.S. fire hit a civilian minivan being used as an ambulance and struck him in the head.

"Terry Lloyd died following a gunshot wound to the head. The evidence this bullet was fired by the Americans is overwhelming," Walker said. "There is no doubt that the minibus presented no threat to the American forces. There is no doubt it was an unlawful act of fire."

ITN cameraman Daniel Demoustier, the sole survivor of the incident, told the inquest ITN's two four-wheel drive vehicles were overtaken by a truck carrying Iraqi forces and that gunfire erupted.

Demoustier, a Belgian, said he jumped from the flaming car and lay in the sand, waiting for the shooting to stop. Demoustier said he tried to stand to signal U.S. tanks in the area but they resumed firing at the clearly marked ITN vehicles.

Demoustier said he saw a makeshift ambulance arrive and pick up people. He was later taken to safety in the car of a British newspaper reporter.

The coroner said Friday that an Iraqi civilian drove up in a minivan and picked up four wounded Iraqi soldiers, then saw Lloyd with a press card around his neck and helped him into the van. Lloyd was shot in the head as the van drove toward a hospital, the coroner said.

In an interview with The Associated Press, Demoustier said after the ruling that the inquest did not make clear whether the bullet that killed Lloyd was fired by a U.S. tank or helicopter. He said the forces in a tank would have been able to see that they were firing at a civilian vehicle, but a helicopter would not.

Lloyd's widow, Lynn, in a statement read by her lawyer, said U.S. forces "allowed their soldiers to behave like trigger-happy cowboys in an area in which there were civilians traveling."

Lloyd and the three other ITN crew members were some of the few Western reporters who covered the fighting on their own, while most others were embedded with U.S. or British forces.

Lebanese interpreter Hussein Osman also was killed and cameraman Fred Nerac remains missing and presumed dead.

U.S. authorities didn't allow servicemen to testify at the inquest. Several submitted anonymous statements that the coroner ruled inadmissible.

"I should have heard all evidence from the American personnel," Walker said. "It was not satisfactory or appropriate to read these statements in place of that evidence."

The court watched a video Tuesday, filmed by a U.S. serviceman attached to one of the tanks accused of firing at the reporters' cars. The tape opens with images of Lloyd's vehicle and the Iraqi truck burning amid gunfire. The tanks drive to the cars and inspect them. A minivan — possibly the ambulance — appears and more shots are fired. At the end of the tape, a U.S. soldier shouts, "It's some media personnel! That's media down there!"

A forensic examiner said the first 15 minutes of the tape may have been erased.