By filming James Foley’s murder and distributing the video across the internet, the Islamic State appalled a world already grown accustomed to the nightmare horrors of terrorism. Al Qaeda executed a violent campaign in Saudi Arabia in 2003 and 2004 reminiscent of that of the present-day Islamic State. Images of executions bring terrorism and the fear it engenders into the homes of everyone who sees them. It makes terrorism far more personal.

For me, Foley’s tragic death brought back haunting memories from my work in the Foreign Service.

In 2004, I was serving as the deputy chief of mission – second in charge after the ambassador – at the American Embassy in Riyadh, Kingdom of Saudi Arabia. Since May of 2003, the Kingdom had been wracked by a series of terrorist attacks, ostensibly the responsibility of what became known as Al Qaeda in the Arabian Peninsula (AQAP). Diplomats, the expatriate business community, foreign workers and even Saudi citizens had become increasingly worried by the attacks, which included bombings of and attacks on western residential and business compounds and Saudi facilities.

By late 2003, we started seeing something different. The attacks became personal. Rather than targeting large, fortified and well-guarded facilities, the terrorists targeted individuals, mostly Westerners but others as well.

The first frightening example was a May 2003 attack on Yanbu, a major oil facility on the Red Sea coast, killing six Westerners and a Saudi. Later that month, a residential compound in Khobar, in the Kingdom’s Eastern Province and a center for the oil and gas industry, was the target. It was terrifying as the terrorists went house-to-house, searching for non-Muslims and even testing Muslims of their knowledge of the Quran. The dead included 19 foreigners and three Saudis; 25 were wounded.

I remember speaking with a survivor of the Khobar attack, who told me that she had stared in abject horror as the terrorists ran down the compound’s streets. “I saw them. I saw their eyes. They were determined to kill.” She had seen one woman running with her child, both pursued by killers. “They wanted to kill them.”

The rampage continued in Riyadh. First, a German chef was gunned down at an ATM machine in May. In early June, a BBC cameraman was murdered in a Riyadh neighborhood; the BBC correspondent, Frank Gardner, was severely wounded. Then, three Americans were killed in separate incidents close to their homes or places of work.

The one I remember most was Paul Johnson, an employee of Lockheed Martin in Riyadh. Johnson was kidnapped and later beheaded. Before his death, his kidnappers had produced a video threatening to carry out his execution.

Finally, on June 18, 2003, the Saudi security forces tracked down in a Riyadh suburb and killed the man responsible for these attacks and the professed leader of AQAP, Abdul Aziz al Muqrin.

Al Muqrin had been enemy number one in the Kingdom since the previous year. A veteran of fighting in Soviet-occupied Afghanistan, Algeria, Bosnia and the Horn of Africa, he was a diabolical master of terrorism. He understood that to achieve real terror, people had to feel genuinely afraid. Large-scale attacks on buildings, compound bombings, and the like made the odds too small for the average person to feel threatened, even in Saudi Arabia where such attacks were becoming common place.

Al Muqrin took terrorism into people’s homes and offices. His filming allowed him to confront people and challenge them to accept his way or die. No longer something people read or heard about, terrorism was something everyone feared now because one could easily visualize becoming the victim.

His strategy worked. Riyadh was gripped with fear. Until then, Saudi Arabia had been one of the safest countries in the world. Violent crime was rare, not only because of the harsh penalties of Saudi sharia law but also because of the nature of Saudi society.

But not after al Muqrin. People talked about arming themselves and what they would do if threatened by al Muqrin and his murderous gang. Foreign embassies, including the American, evacuated non-essential staff and dependents. Many international businesses withdrew their employees and families.

Al Muqrin’s reign of terror was thankfully brief. But his insidious brand of terrorism continued. In August, terrorists stormed the US Consulate General in Jeddah. Following al Muqrin’s modus operandi, the terrorists went building-to-building looking for victims, who were shot on site but not before having to face their murderers.

Survivors described to me their alarm as they watched the terrorists scour the compound for Americans. After an eight-hour ordeal, Saudi Special Forces finally entered the compound and killed all but one of the terrorists.

Most frightening was what they discovered: the terrorists had planned to film each one of the Americans they killed.

Thankfully, Americans escaped that day, due to the heroic efforts of our Marine Security Guard and, in several cases, our foreign national staff. But five foreign national staff members were killed.

Now under the banner of the Islamic State, I again see the face of al Muqrin – confronting innocents with ruthless terrorism. James Foley, like thousands of Syrians and Yazidis and other minorities of northern Iraq, also has seen terrorism’s face. And so have we. Filming these executions brings the fear they engender into the homes of everyone who watches them.

Al Muqrin could only have dreamed of the fighters, wealth and weaponry of today’s counterpart, Abu Bakr al-Baghdadi, the self-appointed caliph of the Islamic State. He has perfected al Muqrin’s strategy, becoming a murderer on a mass scale and instilling individualized fear on an equally mass scale.

Chairman of the US Joint Chiefs of Staff General Martin Dempsey’s characterization of the Islamic State’s “apocalyptic, end-of-days strategic vision” is no exaggeration. The US and other nations would be wise to take this threat every bit as seriously as we did Al Qaeda, bin Laden, and al Muqrin.

Given the wide swath of territory they now control, the increased recruiting draw of their successes and accumulated resources, al-Baghdadi and the Islamic State are onto a winning, if horrendous, strategy. They won’t stop in Syria and Iraq.