The military investigation into the deadly attack during the Afghanistan evacuation has concluded that a suicide bomber acted alone and that the deaths of more than 170 Afghans and 13 US service members were not preventable.
The blast at Abbey Gate outside the Kabul airport on 26 August killed 11 US Marines, a sailor and a soldier, who were screening the thousands of Afghans desperately trying to get onto one of the crowded flights leaving the country after the Taliban takeover.
The so-called Islamic State group claimed responsibility for the attack.
At the Pentagon on Friday, military officials laid out a detailed and graphic minute-by-minute account of the bombing.
The bottom line, they said, was that those who died had wounds that were "so catastrophic” that they could not be overcome. They also stated that earlier thoughts that it was a complex attack involving gunfire turned out to be unfounded.
“A single explosive device killed [by] directing ball bearings through a packed crowd and into our men and women at Abbey gate,” said General Frank McKenzie, head of US Central Command.
“The disturbing lethality of this device was confirmed by the 58 US service members who were killed and wounded despite the universal wear of body armour and helmets that did stop ball bearings that impacted them, but could not prevent catastrophic injuries to areas not covered.”
Investigators said the bomber likely got near the gate by bypassing Taliban and other security checkpoints.
They said it appears the Taliban did not know of the attack, that security precautions were being taken, and that intelligence about potential threats circulating that day was not specific.
“Based upon our investigation, at the tactical level this was not preventable,” said Brigadier General Lance Curtis who led the investigation.
He added that military leaders on the ground in Kabul followed proper security measures, at times closing the gate or pausing the processing of evacuees.
Military officials said that gunfire after the blast was found to be warning shots fired by US and British troops and that no one was killed or wounded by gunshots.
'Instant chaos and sensory overload'
McKenzie said the investigation revealed that the five-millimetre ball bearings in the 10-kilogramme bomb caused wounds that looked like gunshots. He said some troops in the area fired a number of warning shots, and that led others to believe that the attack also included gunmen.
Friday's briefing lasted more than an hour and resembled the detailed explanations military officials gave to the families of the troops killed that day. It included several videos of the chaos at the gate at the time of the bombing.
One is very brief and shows two Marines in the foreground, and deep in the background between them is a glimpse of a single person, dressed all in black.
And then there is the sound of an explosion, and a cloud of black smoke rises from that area. Investigators said the bomber was likely standing on the far side of a sewage canal and was a bit “elevated” when detonating the bomb. Pieces of a backpack were found.
Three service members who were standing on a short wall looking over the crowd to identify potential evacuees were just 10 feet from the blast and were killed.
Longer videos shot from overhead show Marines and others rushing to treat and evacuate the wounded, providing first aid and carrying people over their shoulders as they ran, while civilians scrambled to flee the area.
Marines cut holes in the adjacent fence so they could get to triage areas more quickly, while also struggling through a fog of tear gas that enveloped the area when the bomb fragments punctured the canisters troops carry.
The blast, said investigators, created “instant chaos and sensory overload.” But within 20 minutes all of the killed and wounded had been moved to triage sites.
The nearly 20 pages of briefing documents included photos showing the crush of Afghans and others trying to get cleared into the airport, many waving documents and slogging through the sewage trench to get closer to the troops processing evacuees.
Investigators said that as the Taliban made it more difficult to get through checkpoints, Afghans and others began using side roads and back alleys to get closer to the outer gate.
The investigation also concluded that there was enough medical staff and blood at several sites around the airport, including nine surgical teams and a hospital.
It also quoted a trauma surgeon who told investigators that “We had all we needed. Did we need more people? No, we had a lot of experience on the team and plenty of people".
The number of service members wounded in the bombing grew to 45 in the following days as they were examined and some were found to have traumatic brain injuries from the blast.
Overall, the US-led coalition evacuated about 126,000 people in about three weeks, and the US left Afghanistan for the last time at about midnight on 30 August.
Early on, McKenzie said troops at the gates had to get close to the people they were screening.
“This is close up work. The breath of the person you are searching is upon you,” McKenzie said in August soon after the attack.