A British coroner investigating the "friendly fire" killing of a British soldier by a U.S. warplane during the invasion of Iraq in 2003 ruled Friday that the death was a "criminal" act.

"I don't think this was a case of honest mistake," said Oxfordshire Assistant Deputy Coroner Andrew Walker, concluding his probe into the death of Lance Cpl. Matty Hull, 25. Walker, who had earlier blasted an "appalling" lack of cooperation from the U.S. military, said he believed the pilots who fired on Hull's convoy did not take steps to identify their target that they "could easily have taken."

Hull's death and the U.S. military's initial refusal to release a cockpit videotape showing it have caused anger in Britain and created friction between Washington and its closest ally in the Iraq war. U.S. officials have called the incident a tragic mistake and said that U.S. military authorities have cleared the pilots, who have not been publicly identified, of any wrongdoing.

"We're disappointed in the language used in the decision," David Johnson, deputy chief of mission at the U.S. Embassy in London, said in an interview.

Johnson said that separate investigations by the U.S. and British militaries had concluded that the pilots did not violate any military procedures or regulations. He said the incident was an accident and that "our hearts go out" to the soldier's family.

Susan Hull, the soldier's widow, said the verdict proved that "Matthew's death was entirely avoidable."

The coroner's report would only be used as the basis for further legal action if the family chose to pursue it, according to a spokesman for the coroner's office. Hull on Friday said she and her family would "move on" from the incident and said she hoped the pilots involved "are at peace with themselves" and can "move on with their lives."

"I'm sure they are full of remorse for what they did -- I hope so, anyway," Hull said.

Hull also said that her husband and the British military had been "badly let down" by the United States.

The U.S. government rarely releases video and audio recordings of friendly fire incidents, and it initially declined to provide such evidence for the inquiry into Hull's death. But last month a British tabloid newspaper posted the cockpit video, which it had obtained from unidentified sources, on its Web site.

In the video, the U.S. pilots are heard reacting with horror and disbelief when they realized they had killed a friendly soldier. One of the pilots, from the 190th Fighter Squadron of the Idaho Air National Guard, is heard saying, "I'm going to be sick" and "We're in jail, dude."

Hours after the video was posted, the Pentagon agreed to release the video to the coroner and the family, who later viewed it.

The 15-minute video shows the view forward from the cockpit of an A-10 Thunderbolt attack jet, as well as computerized flight data. It also contains audio of the voices of the jet's pilot, the pilot of another A-10 flying in tandem, the voices of several U.S. ground controllers and the sounds of the attacking aircraft's guns.

On the tape, the pilots are heard discussing orange panels they observed atop the vehicles they were preparing to attack. Vehicles in the invasion force were marked with orange panels visible from the sky. Assured by ground controllers that there were no friendly vehicles in the area, one of the pilots on the tape concludes that the orange panels are actually rocket launchers on enemy vehicles. He then strafes the vehicles twice with rapid-fire cannons before realizing the mistake.

In his ruling Friday, Walker concluded that the pilots "broke with the combat rules of engagement in failing to properly identify the vehicles and seek clearance before opening fire."

"The pilot chose to interpret the orange panels as rockets without taking steps to identify the vehicles as friendly," Walker said, adding that the pilots had no "lawful authority" to fire on the convoy and therefore had committed a criminal act "outside the protection of the law of armed conflict."

Walker also said that he believed "the full facts have not yet come to light."

Johnson of the U.S. Embassy said that all relevant information had been turned over by U.S. authorities.

He said Walker requested information about U.S. forces' rules of engagement in combat. Johnson said that request was refused because "it gives a paint-by-numbers kit to your current and potential adversaries."

Johnson said he believed Walker, "does not have a good grounding in the law of armed conflict."