According to President Obama Thursday, an American and an Italian hostage being held captive by al Qaeda near the border of Pakistan and Afghanistan were accidentally killed by a United States counterterrorism operation in January.

The White House said that American doctor Warren Weinstein and Italian aid worker Giovanni Lo Porto were inadvertently hit by a drone strike.

They said that American al Qaeda leader Ahmed Farouq and American al Qaeda operative Adam Gadahn also died as a result of the attack.

“I profoundly regret what happened. On behalf of the United States government, I offer our deepest apologies to the families,” Obama said in the Brady Press Briefing Room.

“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,” he added.

While the details remain classified (Obama said that he put in an order to declassify them, however) the target was believed to be a terrorist compound with no civilians present.

More from Reuters:

Weinstein, 73 was abducted in Lahore, Pakistan, in 2011 while working for a U.S. consulting firm. Al Qaeda had asked to trade him for members of the Islamist militant group being held by the United States.

Weinstein was seen in videos released in May 2012 and December 2013, asking for Obama to intervene on his behalf and saying he was suffering from heart problems and asthma.

Lo Porto had been missing in Pakistan since January 2012.

“As a husband and as a father, I cannot begin to imagine the anguish that the Weinstein and Lo Porto port families are enduring today … I know that there is nothing that I can ever say or do to ease the heartache,” Obama said.

The White House said that while the operation “was lawful and conducted consistent with our counterterrorism policies, we are conducting a thorough independent review to understand fully what happened and how we can prevent this type of tragic incident in the future.”