The mob grew more frenzied as the gunmen dragged the two surviving Americans from the cab of their bullet-ridden lorry and forced them to kneel on the street.
Killing one of the men with a rifle round fired into the back of his head, they doused the other with petrol and set him alight. Barefoot children, yelping in delight, piled straw on to the screaming man’s body to stoke the flames.
It had taken just one wrong turn for disaster to unfold. Less than a mile from the base it was heading to, the convoy turned left instead of right and lumbered down one of the most anti-American streets in Iraq, a narrow bottleneck in Duluiya town, on a peninsular jutting into the Tigris river named after the Jibouri tribe that lives there.
As the lorries desperately tried to reverse out, dozens of Sunni Arab insurgents wielding rocket launchers and automatic rifles emerged from their homes.
The gunmen were almost certainly emboldened by the fact that the American soldiers escorting the convoy would not have been able to respond quickly enough.
“The hatches of the humvees were closed,” said Capt Andrew Staples, a member of the Task Force Liberty 1-15 battalion that patrols Duluiya and other small towns on the eastern bank of the Tigris, who spoke to soldiers involved.
Within minutes, four American contractors, all employees of the Halliburton subsidiary Kellog, Brown & Root, were dead. The jubilant crowd dragged their corpses through the street, chanting anti-US slogans. An investigation has been launched into why the contractors were not better protected.
Perhaps fearful of public reaction in America, where support for the war is falling, US officials suppressed details of the Sept 20 attack, which bore a striking resemblance to the murder of four other contractors in Fallujah last year.
Duluiya, located in the notorious Sunni triangle, is much smaller than Fallujah but no less violent, even if events here rarely make the news.
The violence here seems to encapsulate the growing difficulties the US military is facing in trying to defeat the insurgency. Pinned down by a constant stream of hit-and-run attacks from former Saddam regime loyalists, American soldiers are unable to focus their attention on the foreign extremists who pose a far more dangerous threat to the future of Iraq.
Yet it is here that the battle against the suicide bombers must be won.
The isolated towns east of the Tigris supply the foreign fighters and their allies and provide a haven where they can regroup after American offensives on their urban strongholds.
If the Americans do not close off these boltholes, it seems unlikely the war can be won.
But hopes for progress are growing more remote. The insurgency in eastern Salahuddin province is growing more intense, more deadly and more sophisticated.
Lt Col Gary Brito, the battalion’s commanding officer, said that in recent months the number of roadside bombs targeting his men had increased by a third – even though journeys out of base have been cut back. They are having a more devastating effect too.
“Before only two out of 10 used to be effective,” he said. “Now four or five have a catastrophic effect, blowing away a vehicle or causing casualties.” In the past few months at least four American soldiers in this battalion alone have been killed. Another 39 have been wounded.
Even routine patrols are fraught with danger.
“What the hell was that,” shouted Lt Chris Baldwin as a huge explosion rocked Baker Company’s convoy of humvees trundling along a street in Dour, another town under Lt Col Brito’s watch.
“Contact! Contact!” he bellowed into his radio as the gunners opened fire on a row of nearby houses from where the rocket-propelled anti-tank missile was fired.
As the gunfire died down, the soldiers burst into house after house, their facades peppered with bullet holes.
But, as is so often the case, the attacker had vanished down one of Dour’s maze-like alleys.
Instead the Americans were confronted with sullen Iraqis, holding their terrified children to their sides. An old woman sat on her bed, clutching her heart, as the soldiers interrogated the family.
“They heard nothing, they saw nothing, same as ******* usual,” said Sgt Jody Miller. Taking another deep drag from his cigarette, he turned to the company’s translator.
“Tell them to tell us where the bad guys are so we stop frigging shooting up their houses,” he said.
Nobody was hurt but the mutual distrust between the Americans and the local community deepened just a little bit more.