Lone Suicide Bomber with 'Disturbing Lethality' Carried Out Kabul Airport Attack, US Military Says

The blast outside the Kabul airport that killed 13 American troops in August was caused by a single suicide bomber, despite initial descriptions from U.S. officials that it was a "complex" attack, military officials said Friday as they unveiled the findings of an internal investigation into the attack.

Military investigators also determined that the attack was "not preventable" in spite of indications of threats to the airport beforehand.

"The investigation found that a single explosive device killed at least 170 Afghan civilians and 13 U.S. service members by explosively directing ball bearings through a packed crowd and into our men and women at Abbey Gate," U.S. Central Command chief Gen. Frank McKenzie said in opening remarks at a press briefing about the investigation. "The disturbing lethality of this device was confirmed by the 58 U.S. service members who were killed and wounded despite the universal wear of body armor and helmets that did stop ball bearings that impacted them but could not prevent catastrophic injuries to areas not covered."

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Eleven Marines, one soldier and one sailor became the last U.S. fatalities in America's 20-year war in Afghanistan following the Aug. 26 suicide bombing outside of Hamid Karzai International Airport. The U.S. military was conducting an evacuation at the airport as throngs of Afghans desperate to flee the Taliban amassed outside and pleaded with troops to be among those flown out to safety.

The attack has been attributed to the Afghan branch of ISIS, known as ISIS-Khorasan.

Another 45 service members were injured in the attack, according to the newly released investigation findings. That's an increase from the 26 officials initially said were injured, a difference investigators attributed Friday to later screenings for traumatic brain injuries.

U.S. officials had also initially said the bombing was followed by militants opening firing into the crowd.

But on Friday, officials said that was a mistaken assessment fueled by the chaos of the scene, as well as ball bearing injuries that resembled gunshot wounds and the fact that Marines and British service members fired warning shots after the bombing.

Investigators, led by Army Brig. Gen. Lance Curtis, interviewed 139 people and reviewed 250 exhibits to reach their findings, Curtis said Friday. No Afghan witnesses were interviewed, investigators said, citing the difficulty of doing so after the military withdrew from Afghanistan four days later.

"Based upon our investigation at the tactical level, this was not preventable," Curtis said. "The leaders on the ground followed the proper measures. And anytime there was an imminent threat warning, they followed the proper procedures. They lowered their profile, they sought cover and, at times, they even ceased operations at the gate."

On the day of the attack, the only entrance to the airport that was open was Abbey Gate. The day before, the East Gate was closed because the geography made it difficult to process evacuees, and the North Gate was closed because of threats of car bombs, Curtis said Friday.

At Abbey Gate, the Taliban was providing security atop shipping containers made into a chevron-shaped barrier set up by U.S. forces Aug. 20 to protect against possible car bomb threats. About 200 yards down from the chevron was an outer gate Marines used as a holding area for potential evacuees, and another 300 yards down was an inner gate.

But as the Taliban became less cooperative at the chevron and were turning away, beating or shooting at potential evacuees, Afghans were given maps by American service members, U.S. government officials and private organizations to bypass the Taliban checkpoint. The routes took potential evacuees to a parking lot, where, as desperation grew, Afghans then used a sewage canal to get closer to the gates.

Investigators believe it was "highly likely" the suicide bomber used one of those alternate routes so he would not have to show identification to get close enough to U.S. service members to detonate his device, said Marine Corps Lt. Col. John Naughton, one of the investigators.

In a video shown at the briefing, someone dressed in black and believed to be the bomber is seen in the distance behind a Marine in the foreground. In a flash, the individual disappears in a plume of smoke, and the Marine, who was about 48 meters away from the blast, turns to look before ducking for cover from the force of the explosion.

After the bombing, about 25 to 30 rounds were fired from an area where British forces were located and four rounds were fired by Marines over the head of someone who displayed "concerning behavior," investigators said. Separately, a team of Marines saw a man with an AK-47 assault rifle they believed "exhibited hostile intent" and fired toward him, though the Marines never saw him fire his weapon.

Despite the gunfire, investigators said they found "no definitive proof" anyone was hit or killed by bullets.

"Marines experienced mental and physical friction," said Marine Col. C.J. Douglas, another of the investigators. "Several interviews discuss the presence of tear gas, which was released when the CS canisters worn on the Marines equipment were punctured by ball bearings from the blast. At this point, Marines were simultaneously enduring tear gas and blast effects while responding to a mass casualty situation. Plainly put, the blast created instant chaos and sensory overload."

Officials had been aware of four "threat streams" ahead of the attack and took what investigators described as appropriate measures in response. But the threats were "not specific," investigators added.

There were several discussions about whether to close Abbey Gate, including at a meeting about half an hour before the bombing, between a U.S. brigadier general, British forces and the Taliban, investigators said Friday. But officers kept the gate open to continue identifying Afghans in the crowd to evacuate. The coalition forces were working on evacuations while still trying to prevent another breach of the airport and rushing of the runway like happened Aug. 16 when Afghan civilians rushed an American plane, several clinging to the sides of the aircraft and falling to their deaths when it took off.

Marines were concentrated on one area the day of the bombing to help control an increasingly desperate and aggressive throng of Afghans, which investigators said was exemplified by a video shown at the briefing of a Marine being pulled into the crowd by the muzzle of his rifle the day before the attack.

"The investigation found that military leadership on the ground was appropriately engaged on force protection measures throughout the operation of Abbey Gate and that the medical services that were available, and that were ready, saved every life they possibly could through heroic efforts," McKenzie said. "While nothing can bring back the 11 Marines, the soldier and the sailor that we tragically lost in this attack, it's important that we fully understand what happened. Their sacrifice demands nothing less."

-- Rebecca Kheel can be reached at rebecca.kheel@military.com. Follow her on Twitter @reporterkheel.

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