From the safe haven room where Stevens, Smith and the agent were hiding they could see the men roaming throughout the house, trying to open grates, looking for them.
When the men didn't find anyone, they poured diesel fuel all over the rooms and furniture, setting the house on fire. As black smoke, diesel fumes and fumes from the burning furniture filled up the safe haven, the three tried to get to the bathroom area where there was a small window to open it for air, which did not help.
At this point, the official said, the security officer, Smith and the ambassador were on the ground gasping for air and suffering from "severe" smoke inhalation and decided to take their chances and get out of the safe haven and building.
The security agent led the way, but when he got outside he realized that neither Smith nor the ambassador had made it after him.
He went back in several times to find them, but eventually had to leave because he was overcome by the strong smoke. He climbed to a safe area outside of the building and radioed for help.
Meanwhile the other agents in the compound had gone to Building B to get helmets, body armor and their "long guns." They headed back, but after encountering a large group of armed men, they decided to head back to Building B to barricade themselves, and the two agents in the TOC did the same.
The attackers unsuccessfully attempted to enter both buildings, but failed.
After the agent in Building C's unsuccessful attempt to find his colleagues he radioed to the other four that building C was on fire. This was the first time they realized the building was on fire.
A quick reaction security team of six agents from the building roughly a mile away, known as the "annex," arrived at the compound with 16 members of the local Libyan militia, the 17th of February Brigade.
They set up a perimeter around Building C, where Stevens and Smith were still inside, which allowed the two agents to take over the task of looking for Stevens and Smith.
Under heavy, thick black smoke the agents took turns looking for the missing diplomats, feeling their way around on their hands and knees. They finally found Smith dead, and pulled him out, but did not find Stevens.
Outnumbered by "an unbelievable amount of bad guys" in the compound the militia fighters told the security team they had to evacuate, according to the State Department official.
"We've got to leave, we can't hold the perimeter," the official said the militia told the team.
The security team then loaded up into an armored vehicle and headed slowly to the annex building. They took heavy fire as they emerged from the compound's main gate and turned back twice upon encountering crowds and small groups of armed men.
They came upon a group of armed men in an adjacent compound who motioned them to turn inside. The official said the agents "smelled a rat and stepped on it," taking heavy fire at short range, which damaged the armored vehicle. Despite two flat tires, they kept moving, and when they were stopped again, this time by traffic, the team careened over a median and drove against traffic until they reached the annex.
But the annex was not safe either, and began to come under intermittent AK-47 and RPG fire for the next several hours.
By that time a team of security reinforcements had arrived at the annex in Benghazi from the U.S. embassy in Tripoli aboard a chartered aircraft to help with the fight.
At 4 a.m., the annex took "precise" mortar fire with some of the rounds landing on the roof, immediately killing Glen Doherty and Tyrone Woods and severely wounding another security officer, official said.
At this point the U.S. team was outmatched and a decision was made that they would have to evacuate the annex, the official said. The next hours were spent securing the annex and moving everyone to the airport in Benghazi, where they were evacuated on two flights back to Tripoli.
Stevens was not seen by the security team again until his body was delivered to the airport, officials said, and they still do know how he reached the Libyan hospital where attempts were made to treat him.
Officials said that, in fact, they were informed that Stevens was at the hospital only after doctors found his cell phone and began phoning people on his recent call list.