Today, Robert Mueller heads the investigation into Russian collusion in the 2016 U.S. presidential election. At Wired, Garrett M. Graff reports on one of Mueller’s perhaps lesser-known but nonetheless fascinating and insightful previous assignments: at one time, Mueller oversaw the U.S.’ investigation into the bombing of Pan Am flight 103.

The bombing, which took place over Lockerbie, Scotland, in December 1988, was the first act of terrorism against U.S. civil aviation. To this day it remains “the largest crime scene ever investigated” and revealed how woefully unprepared the FBI and the U.S. government were to respond to the families of terror victims.

The time on the clocks in Lockerbie, Scotland, read 7:04 pm, on December 21, 1988, when the first emergency call came into the local fire brigade, reporting what sounded like a massive boiler explosion.

Soon it became clear something much worse than a boiler explosion had unfolded: Fiery debris pounded the landscape, plunging from the sky and killing 11 Lockerbie residents. As Mike Carnahan told a local TV reporter, “The whole sky was lit up with flames. It was actually raining, liquid fire. You could see several houses on the skyline with the roofs totally off and all you could see was flaming timbers.”

At 8:45 pm, a farmer found in his field the cockpit of Pan Am 103, a Boeing 747 known as Clipper Maid of the Seas, lying on its side, 15 of its crew dead inside, just some of the 259 passengers and crew killed when a bomb had exploded inside the plane’s cargo hold.

It had taken just three seconds for the plane to disintegrate in the air, though the wreckage took three long minutes to fall the five miles from the sky to the earth; court testimony later would examine how passengers had still been alive as they fell. Nearly 200 of the passengers were American, including 35 students from Syracuse University returning home from a semester abroad. The attack horrified America, which until then had seen terror touch its shores only occasionally as a hijacking went awry; while the US had weathered the 1983 bombing of the Marine barracks in Beirut, attacks almost never targeted civilians.

The Pan Am 103 bombing seemed squarely aimed at the US, hitting one of its most iconic brands. Pan Am then represented America’s global reach in a way few companies did…

The bombing soon became one of the top cases on Mueller’s desk. He met regularly with Richard Marquise, the FBI special agent heading Scotbom. For Mueller, the case became personal; he met with victims’ families and toured the Lockerbie crash site and the investigation’s headquarters. He traveled repeatedly to the United Kingdom for meetings and walked the fields of Lockerbie himself.

The Scotbom case would leave a deep imprint on Mueller; one of his first actions as FBI director was to recruit Kathryn Turman, who had served as the liaison to the Pan Am 103 victim families during the trial, to head the FBI’s Victim Services Division, helping to elevate the role and responsibility of the FBI in dealing with crime victims.

Read the story