New details were emerging about how the US learned, and announced this week, the pair of deadly drone strikes had killed hostages Warren Weinstein and Italian Giovanni Lo Porto and the two al-Qaida operatives.
The drone strike was ordered because officials believed there were four members of al-Qaida's leadership in the building in the tribal areas of northern Pakistan.
But they later learned six bodies had been buried instead of the four they expected, two US officials said, speaking on condition of anonymity because they weren't authorised to discuss the matter publicly.
Coincidental intelligence emerged that Weinstein, a contractor with the US Agency for International Development who was captured in 2011, was dead, but intelligence officials didn't know how, when or where.
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They began investigating, parsing through intercepts, and interviewing local sources in Pakistan, the officials said. It wasn't until two weeks ago that they got the crucial piece of intelligence that led them to conclude that Weinstein and Lo Porto were killed in the January strike.
"It is a cruel and bitter truth that in the fog of war generally and our fight against terrorists specifically, mistakes, sometimes deadly mistakes, can occur," President Barack Obama said.
The Pakistan Ministry of Foreign Affairs today issued a statement of condolences to the hostages' families.
"Having lost thousands of innocent civilians in the war against terrorism, Pakistan can fully understand this tragic loss and stands with the families of Weinstein and Lo Porto in this difficult time," the ministry said.
Meanwhile, in Italy, Foreign Minister Paolo Gentiloni is seeking to explain to Parliament why it took three months to learn about the death of Lo Porto in the U.S. Drone strike. Gentiloni told lawmakers Friday that in an inaccessible war zone, where hostage-taking is frequent, it took that long for US intelligence to verify Lo Porto had been killed.