Updated at 1 p.m. ET
U.S. personnel "could not have predicted" dozens of Mosul residents would be in a building from which ISIS snipers were attacking Iraqi forces, the Pentagon says, in its report on a U.S. air strike that killed at least 105 civilians. The report also says the building collapsed after the strike triggered explosives that had been planted by ISIS.
The report provides new details about a strike that devastated several families and prompted rights groups to accuse the U.S.-led coalition of not taking adequate precautions to protect people in Mosul.
It wasn't until after the attack that officials learned civilians were in the targeted building. Between 101 and 137 people are believed to have sought refuge there, according to an executive summary of the report prepared for the commander of Operation Inherent Resolve.
Of the casualties, 101 civilians died in the structure; another four people died from damage to the neighboring building, the Pentagon says.
The strike had targeted two ISIS snipers who were on the building's second floor; the U.S. bomb was expected to damage no more than 20 percent of the structure, the Pentagon says. Instead, the building was reduced to a crater of rubble, after ISIS-emplaced explosives detonated, the report says.
The Pentagon says the home that was hit on March 17 either was used to store bombs or was rigged with explosives that "conservatively contained more than four times the net explosive weight" of the 500-pound munition (with 192 pounds of explosive material) that was dropped on the building.
The report summary says that the munition, described as "GBU-38 with a delayed fuse," was chosen by the coalition's Target Engagement Authority in the belief that it would achieve "the necessary effect and minimize collateral damage."
The civilians had been forced out of their houses and invited into the home by its owner, the report says. It adds that ISIS fighters had interacted with the residents — and that one next-door neighbor had told investigators that ISIS fighters had warned him to evacuate his family and move north by the morning of March 17 to avoid danger.
The Pentagon's summary was prepared by the investigating officer, Air Force Brig. Gen. Matthew C. Isler.
After the strike, Iraqi rescue workers told NPR they found dozens of bodies in the rubble. Coming amid a new offensive to try to retake Mosul from ISIS, the attack set off a debate over how to prevent civilian casualties when people are used as human shields — and whether the U.S.-led coalition has been cautious enough in its attacks.
Survivors of the strike told NPR's Jane Arraf about the devastating losses they suffered, and why they hadn't been able to leave.
"Three times we tried to leave and ISIS sent us back," Ala'a Hassan told Jane. "They fired in the air and in the end they said if you try to leave we will hang you."
The deaths prompted Amnesty International to accuse the U.S.-led coalition of not taking adequate precautions to protect people in Mosul, not providing a safe escape route for civilians, and using munitions that are too powerful.
The group's senior crisis response adviser, Donatella Rovera, also acknowledged the challenges in places such as Mosul. Rovera told NPR in March, "There was no easy option because obviously prior to the fighting, Islamic State did not allow people to leave. However, once the fighting got underway, possibilities are created for people to leave."
Within weeks of the strike, as The Two-Way reported, Iraqi and U.S. officials said they would slow the offensive and reduce the number of airstrikes to minimize civilian deaths.