Atiyah Abd al-Rahman was a Libyan national with close ties to late al-Qaida leader Osama bin Laden.

Rahman was on the U.S. State Department's “wanted” list for his ties to the militant group.

Al-Qaida's second in command was believed to have been in his 30's when, the U.S. says, he was killed Monday. The State Department says Rahman was a teenager when he joined bin Laden in Afghanistan in the 1980's.

Over the years, he rose through the ranks of the militant group — serving in roles that included explosives expert, recruiter, liaison and emissary in Iran.

In 2006 the Washington Post said a letter recovered from an al-Qaida safehouse in Iraq placed the group's leadership in Pakistan's border region. The newspaper said the letter was signed “Atiyah.” Counter-terrorism officials believed this was a reference to Rahman.