A signature element of President Barack Obama’s counterterrorism strategy sparked a critical backlash on Thursday, after the commander-in-chief admitted strikes in January along the Afghanistan-Pakistan border resulted in the accidental killing of two innocent hostages, along with the deaths of two American al-Qaida operatives.

Obama took to the White House podium in a briefing Thursday morning to provide some details on the operations three months prior, details of which he has ordered declassified. U.S. officials confirmed in the aftermath of the strikes that aid workers Warren Weinstein, a 73-year-old American from Rockville, Maryland, and Giovanni Lo Porto, an Italian, had been accidentally killed in one strike.

“On behalf of the U.S. government, we offer our deepest apologies to the families,” Obama said. Some aspects of the operation have to remain secret, he said, adding that “the U.S. is a democracy, committed to openness, in good times and in bad.”

“It is a cruel and bitter truth that in the fog of war, generally, and in our fight against terrorists, specifically, mistakes and sometimes deadly mistakes can occur,” Obama said. A willingness to confront mistakes and to learn “sets us apart.”

The president provided no further details on how the strike was conducted – either by a manned airplane or a drone – or whether it was carried out by military personnel or an agency like the CIA. Spending the entirety of the briefing discussing the deaths of the two hostages, Obama also did not provide any further details on the killing of Americans Ahmed Farouq, supposedly an al-Qaida leader killed in the same strike as the hostages, or Adam Gadahn, reportedly an al-Qaida spokesman killed in a separate strike.

The U.S. conducts counterterrorism strikes based on protocols called “near certainties,” White House spokesman Josh Earnest said at a press briefing later on Thursday. These include situations in which officials are highly certain that targets are at the site of a strike, and that there won’t be collateral damage. Earnest said the hostages’ deaths may lead to a change in these protocols.

Warren Weinstein, who died in a January 2015 counterterrorism strike.

AP

The Long War Journal, which tracks strikes in extremist hot spots like Pakistan and Yemen, reported April 12 about a drone strike in Pakistan that killed a person named “Ustad Ahmad Farooq” on Jan. 5, following previous erroneous reports of his death. Farouq belonged to an affiliate of the extremist group called al-Qaida in the Indian Subcontinent, or AQIS, which was founded last September.

The attack that killed Farouq and the hostages was likely a drone strike given the shroud of secrecy that has surrounded it, Bill Roggio, editor at the Journal, tells U.S. News. Previous attempts to send ground troops in for such counterterrorism missions were made public shortly after they took place.

Questions still remain regarding why al-Qaida and its affiliate chose to remain quiet about the deadly strikes in the months since they occurred, Roggio says. Extremists have previously acknowledged some leaders’ deaths and have attempted to capitalize on U.S. strikes that kill civilians, either by broadcasting the outcome as a propaganda coup or using the evidence of such an attack as a bargaining chip against the U.S. government to, for example, release prisoners.

The Pentagon would not offer any further details on the strikes, either. The Air Force largely oversees U.S. drone missions in Afghanistan, a declared war zone, while the CIA is believed to conduct drone strikes in Pakistan.

The Defense Department has been working with other agencies to declassify details of the missions Obama announced Thursday, spokesman Army Col. Steve Warren said.

Obama said Thursday that these strikes comported with the legal authorization used by the U.S. to target al-Qaida operatives and their affiliates abroad.

The U.S. did not know that Weinstein – a U.S. Agency for International Development contractor who was captured in Pakistan in 2011 – and Lo Porto – an aid worker for German organization Welthungerhilfe who was captured in 2012 – were at the site of the strike that killed them, which U.S. intelligence had surveilled for “hundreds of hours,” the president said.

The two American al-Qaida operatives killed in the strikes “were al-Qaida leaders plotting against America as they held hostages,” House Foreign Affairs Committee Chairman Ed Royce, R-Calif., said in a statement.

“Adam Gadahn was a U.S. citizen, raised in California with every possible opportunity and freedom,” Royce said. “And in the end, he spent years trying to destroy our freedoms and encouraging others with hate-filled speech after betraying our country.”