The "emir of suicide bombers," senior Islamic State of Iraq and Syria leader Tariq al-Harzi was killed in Syria by a coalition airstrike last month, according to a Pentagon official.

The 33-year-old Tunisian al-Harzi is believed to be one of the first of the Islamic State's many foreign fighters. He helped raise funds for the militant group from wealthy Gulf patrons, including a $2 million donation from a donor based in Qatar, the Pentagon said.

Harzi also helped procure and ship weapons from Libya to Syria, the Defense Department said. His brother Ali was a person of interest in the Benghazi attacks and was killed by an airstrike in Iraq the day before.

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Critically, Harzi assisted foreign fighters with goods the group sells on the black market, like stolen antiquities, flowing across the Syrian border and was "responsible for moving people and material into Syria and Iraq," according to the Pentagon.

Al-Harzi earned the Pentagon's label "emir of suicide bombers" for his efforts organizing the militants' suicide and vehicle-borne bombs in Iraq in 2013, a tactic they used with devastating effect, according to the U.S. Department of Defense.

The U.S. put a $3-million bounty on his head.

"His death will impact ISIL's ability to integrate foreign terrorist fighters into the Syrian and Iraqi fight as well as to move people and equipment across the border between Syria and Iraq," Pentagon spokesman Navy Captain Jeff Davis said.

"This was a big get," said Mike Rogers, former chairman of the U.S. House Intelligence Committee. "It will be very disruptive to their operation for at least some period of time."

Al-Harzi was killed before the recent spate of Islamic State attacks last Friday in Kuwait, Tunisia and France.