Story highlights Mullah Abdul Rauf was a Taliban commander released from Guantanamo Bay by the U.S. in 2007

He became a recruiter for ISIS in Afghanistan, reports say

He was killed Monday in a drone strike, two officials say

(CNN) He was a Taliban commander captured by the United States and held at Guantanamo Bay. But he was let go and returned to Afghanistan. Mullah Abdul Rauf went on to become a recruiter for ISIS in Afghanistan.

He was killed in a drone strike Monday, two officials told CNN.

Rauf and five others were killed, four of them Pakistani militants, said Mohammed Jan Rasoulya, the deputy governor of southern Helmand province. A senior Afghan security source confirmed Rauf's death.

The Washington Post, in a headline last month , called him "the shadowy figure recruiting for the Islamic State in Afghanistan."

The New York Times called him the "militant commander at the center of the concerns in Helmand Province" but said some local Taliban figures "dismiss claims" that he had established "a significant new Islamic State cell in Helmand Province."

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