BENGHAZI, Libya — An alarm rang around 1 a.m. Wednesday, alerting Libyan emergency room doctor Ziad Bouzaid, 31, that an important patient was en route to Benghazi Medical Center.

Bouzaid, who was working a 24-hour shift, had already seen 10 Libyans come in that evening with various injuries, all saying they had been under attack. In a city inundated with armed militiamen vying for power, rumors were swirling in the emergency room about who was attacking whom.

This time, however, the Libyans who arrived were carrying Christopher Stevens, the U.S. ambassador to Libya. He’s a diplomat, someone said. As Bouzaid began attempting to resuscitate him, he looked at man’s face and recognized the popular ambassador immediately.

“I had seen photos of him on Facebook,” Bouzaid said.

Stevens’ lips were covered in black and his body was “reeking of smoke.”

“There was no sign of life. There was nothing,” Bouzaid said.

Stevens, along with three other Americans, was killed Tuesday in a brazen attack on their consulate compound in Benghazi, the birthplace of the revolution that last year overthrew Moammar Gadhafi.

Stevens, who’d been based in Benghazi throughout the revolt and became the U.S. ambassador to Libya in May, had traveled from Tripoli, where the U.S. Embassy is protected by a unit of U.S. Marines, to the less-protected Benghazi consulate to open a Libyan-American cultural center, a Libyan legislator told a local television station.

Instead, witnesses told McClatchy that attackers launched an assault on the consulate compound that lasted for hours. The attackers, carrying the flag from the Islamist militant group Ansar al Sharia, launched rocket-propelled grenades, setting the building ablaze.

Details of what took place next are still being sorted out. Ansar al Sharia denied responsibility for the attack. The FBI has dispatched agents to Libya to investigate what took place.

What seems clear is what medical aid Stevens received.

Just after midnight Wednesday, Libyan security forces dragged Stevens’ body out of the compound and sped off to the hospital.

Even though he appeared lifeless, Bouzaid said he spent the next 45 minutes trying to revive him.

Bouzaid said his initial assessment was that the ambassador had suffered from suffocation and carbon monoxide poisoning. Patients can survive carbon monoxide levels below 60 percent.

As Bouzaid kept trying to revive him, Stevens’ body only reaffirmed what the doctor already knew. Blood poured out his nose and mouth. “That happens in cases of severe poisoning,” Bouzaid said. Stevens’ carbon monoxide levels were above 60 percent.

“After we were 100 percent sure he was dead, I did my report, and the diplomat went to the morgue,” he said.

It was 1:45 a.m. By 6 a.m., U.S. officials recovered Stevens’ body, Bouzaid said.

Stevens was the only American to arrive in his emergency room that night, even though three others were killed in the attack.

“We tried,” the doctor said.