Before he became U.S. ambassador to Libya, J. Christopher Stevens warned in a 2008 diplomatic cable of jihadist sentiment growing not far from Benghazi.

Stevens, who became ambassador to Libya this year, was killed this week in an attack that U.S. sources tell CNN was planned by a pro-al Qaeda group of extremists. While it is not definitively clear whether this group, or what group specifically, is behind the attack, it's clear that Stevens expressed concern about a radical movement fomenting in the port city of Derna.

The cable was leaked in the trove that WikiLeaks released in 2010 and 2011, and CNN reported on it last year.

In his 2008 missive Stevens, who at the time was U.S. deputy chief of mission in the North African nation, wrote about that "one Libyan interlocutor likened young men in Derna to Bruce Willis' character in the action picture "Die Hard", who stubbornly refused to die quietly."

There is "frustration at the inability of eastern Libyans to effectively challenge" Moammar Gadhafi's regime, Stevens wrote.

That and "a concerted ideological campaign by returned Libyan fighters from earlier conflicts, have played important roles in Derna's development as a wellspring of Libyan foreign fighters in Iraq."

Moammer Gadhafi was killed in October 2011, at the hands of Libyans.

"Other factors include a dearth of social outlets for young people, local pride in Derna's history as a locus of fierce opposition to occupation, economic disenfranchisement among the town's young men. Depictions on satellite television of events in Iraq and Palestine fuel the widespread view that resistance to coalition forces is justified and necessary," Stevens wrote.

Stevens describes Derna: "The lower-middle class neighborhood, comprising poured concrete homes crowded along largely unpaved streets, sits on a hill overlooking the town ... A number of residents were on the streets; however, they were visibly more wary and less friendly than in other Libyan towns."