On the Ansar a-Sharia Brigade being blamed for anti-Western violence in Benghazi, from

Inside the US consulate in Benghazi: material and human damage laid bare
By Chris Stephen in Benghazi, guardian.co.uk, 13 September 2012:  

[....] Benghazi has suffered from activities blamed on jihadists for several months, and anger is directed equally at the protagonists and at a government seen as unwilling to stand up to them.

Last April, a UN convoy carrying the envoy Ian Martin was bombed in the city, followed by attacks on the Tunisian consulate and the office of the International Committee of the Red Cross. Jihadists also wrecked a Commonwealth war graves cemetery in the city, and, though it has been repaired, the vandalised stone cross that formed the cenotaph has not been replaced. In June, the British ambassador, Dominic Asquith, narrowly survived when a rocket missed him and hit the armoured car carrying his security detail, two of whom were wounded.

The Islamist Ansar al-Sharia brigade is blamed by many here for the violence, particularly with the appearance of a video that appears to show two US embassy vehicles plundered from the burning compound being driven into the brigade's Benghazi barracks. Brigade leaders have issued a denial of responsibility but were unwilling to talk to journalists on Thursday.

"They [Sharia] have pros and cons," said Saleh el-Fellah, who works in Benghazi's Friendship Cafe. "They were the ones who provided security [in the revolution]. The cons are all the bad things they have been doing. They take everything to extremes, they are ruining the reputation of Islam."

Sadness is everywhere in the city whose proud boast is that it was the cradle of last year's revolution. A Libyan photographer inside the ruined compound came over to offer an unsolicited apology. "We are not all like this," he insisted. "Libyans do not approve of this." [....]

Yet another view, from a former Libyan fighter (so big cavaet) which agrees with Issandr as regards the idea of Al-Libi retribution; besides the one I quote, the article is loaded at the end with a lot more Libyan sources. That does sync because, if you recall, CNN was the first TV coverage in Benghazi during the "revolution" and spent a lot of time there

Pro-al Qaeda group seen behind deadly Benghazi attack
By Nic Robertson, Paul Cruickshank and Tim Lister, CNN, September 13, 2012

[....]

Noman Benotman, once a leading member of the Libyan Islamic Fighting Group and now based at the Quilliam Foundation in London told CNN, told CNN, "An attack like this would likely have required preparation. This would not seem to be merely a protest which escalated."

"According to our sources, the attack was the work of roughly 20 militants, prepared for a military assault; it is rare that an RPG7 is present at a peaceful protest," Benotman said.

"According to our sources, the attack against the consulate had two waves. The first attack led to U.S. officials being evacuated from the consulate by Libyan security forces, only for the second wave to be launched against U.S. officials after they were kept in a secure location."

[....]

Benotman, who had earlier warned of the likelihood of renewed attacks against U.S. interest in Libya, said the Omar Abdul Rahman Brigades is a prime suspect in the Benghazi attack Tuesday. He believes it is likely the deadly attack was also linked to a video statement released by al-Zawahiri on the 11th anniversary of the 9/11 attacks. In the video, al-Zawahiri confirmed the death of al-Libi -- a prominent member of the al Qaeda-linked group -- adding: "His blood is calling, urging and inciting you to fight and kill the crusaders."

The video released by the Brigades in June showed nighttime explosions around the consulate, interlaced with footage of Osama bin Laden and al-Zawahiri, along with images from the 9/11 attacks. At the time the Brigades claimed it had launched the attack in response to the first reports of al-Libi's death in a drone strike in the tribal areas of Pakistan.

Notably, the Brigades said the June 5 attack was also timed to coincide with preparations for the arrival of a senior U.S. State Department official.

"The time frame of attacks shows that the group has been following and actively involved in gathering information about the activities of diplomatic missions in the country," Benotman wrote in a June briefing paper on the group.

He adds that it appears the Omar Abdul Rahman Brigades was also responsible for a rocket attack against the convoy of the British ambassador in Benghazi on June 11 and an attack against the Red Cross in Misrata on June 12. [....]