Updated

The first Western eyewitness to the deadly Benghazi terror attacks has given an account of the seven-hour assault on the U.S. outpost in Libya and says Americans knew such an incident was inevitable.

The witness -- a former British soldier who for decades helped protect U.S. diplomats and military leaders -- told CBS’ “60 Minutes” that Al Qaeda forces first attacked the U.S. Special Mission Compound in which Ambassador Christopher Stevens was killed. Then they launched a second attack on a secret CIA annex about a mile across the city.

“They knew what they were doing,” the security guard told CBS. “That was a well-executed attack.”

The guard said he was in his apartment about 15 minutes away from the attacks when he learned of them through a frantic phone call from a Libyan guard.

“I could hear gunshots,” said the guard, “And he said, ‘There are men coming into the mission’ … You could tell he was really scared and he was running.”

The guard said that when he asked for details the other guard said: “We're getting attacked. … They're all over the compound."

Stevens and three other Americans were killed in the Sept. 11, 2012, attacks.

Susan Rice, then the U.S. ambassador to the United Nations, and other administration officials said in the days following the attacks that they appeared to have been sparked by an anti-Islamic video posted onto the Internet.

The guard also told CBS that he considered the security forces hired to protect the U.S. interests in Benghazi lax and suggested the attack appeared inevitable.

Fox News has previously reported that an Aug. 16, 2012, cable revealed that an “emergency meeting” was convened less than a month before the assault to warn that the consulate could not defend against a coordinated attack. Congressional hearings held over the past year have also covered how security was a concern in the run-up to the attack.

And Fox News reported last week that, according to a source on the ground in Libya, a former Guantanamo Bay detainee with Al Qaeda ties -- Sufian bin Qumu -- was in Benghazi the night of the attack. Fox News also reported that two other suspects have ties to the Al Qaeda senior leadership -- one believed to be a former courier and the other, a bodyguard for the network.

The guard who spoke with CBS noted that Al Qaeda tried to kill a British ambassador in Benghazi three months before the attack on the anniversary of 9/11. He added that the terror group said online that it would attack the Red Cross, the British, and then the Americans in Benghazi.

“They made good on two out of the three promises,” the guard said. “It was a matter of time till captured the third one. … [Washington] knew we monitored it. We included that in our reports to both State Department and" the Department of Defense.

The guard’s most dramatic account of the hours-long ordeal is when a team from the annex rushed to help fellow Americans under siege at the compound.

“About 30 minutes into the attack, a Quick Reaction Force from the CIA annex  ignored orders to wait and raced to the compound, at times running and shooting their way through the streets just to get there.

"Inside the compound, they repelled a force of as many as 60 armed terrorists and managed to save five American lives and recover the body of Foreign Service Officer Sean Smith. They were forced to fight their way out before they could find the Ambassador" Stevens.