President Joe Biden expressed hope Monday that the killing of al-Qaida leader Ayman al-Zawahri brings “one more measure of closure” to families of the victims of the Sept. 11, 2001, attacks on the United States.

Biden made the comments as he confirmed that a U.S. drone strike in Afghanistan this weekend killed al-Qaida leader Ayman al-Zawahri.

“He will never again, never again, allow Afghanistan to become a terrorist safe haven because he is gone and we’re going to make sure that nothing else happens,” Biden said in an address from the White House formally announcing the operation.

“This terrorist leader is no more,” Biden said.

He said U.S. intelligence officials tracked al-Zawahri to a home in downtown Kabul where he was hiding out with his family. The president approved the operation last week and it was carried out on Sunday.

The following is a special report from CBS News.