Gaining Entrance

Then, around 6:30 p.m., a small group of protesters — one official briefed on the events put it around 20 — brought a ladder to the wall of the compound and quickly scaled it, gaining entrance to the ground. Embassy officials asked the Egyptian government to remove the infiltrators without using weapons or force, to avoid inflaming the situation, this official said. (An embassy official said that contrary to reports on Tuesday, no one fired weapons in the air.) But it took the Egyptian security officers five hours to remove the intruders, leaving them ample time to run around the grounds, deface American flags, and hoist the black flag favored by Islamic ultraconservatives and labeled with Islam’s most basic expression of faith, “There is no god but God, and Muhammad is his prophet.”

It is unclear if television images of Islamist protesters may have inspired the attack in Benghazi, which had been a hotbed of opposition to Colonel Qaddafi and remains unruly since the Libyan uprising resulted in his death. But Tuesday night, a group of armed assailants mixed with unarmed demonstrators gathered at the small compound that housed a temporary American diplomatic mission there.

The ambassador, Mr. Stevens, was visiting the city Tuesday from the United States Embassy compound in Tripoli to attend the planned opening of an American cultural center, and was staying at the mission. It is not clear if the assailants knew that the ambassador was at the mission.

Interviewed at the scene on Tuesday night, many attackers and those who backed them said they were determined to defend their faith from the video’s insults. Some recalled an earlier episode when protesters in Benghazi had burned down the Italian consulate after an Italian minister had worn a T-shirt emblazoned with cartoons mocking the Prophet Muhammad. Ten people were reportedly killed in clashes with Colonel Qaddafi’s police force.

That assault was led by a brigade of Islamist fighters known as Ansar al-Sharia, or the Supporters of Islamic Law. Brigade members emphasized at the time that they were not acting alone. On Wednesday, perhaps apprehensive over Mr. Stevens’s death, the brigade said in a statement that its supporters “were not officially involved or were not ordered to be involved” in the attack.

At the same time, the brigade praised those who protested as “the best of the best” of the Libyan people and supported their response to the video “in the strongest possible terms.”

Conflicting Accounts

There were conflicting accounts of how Mr. Stevens had died. One witness to the mayhem around the compound on Tuesday said militants chased him to a safe house and lobbed grenades at the location, where he was later found unconscious, apparently from smoke inhalation, and could not be revived by rescuers who took him to a hospital.