Before he was President Donald Trump's attorney general, William Barr led the Justice Department under George H.W. Bush and entered office just weeks after the 1988 Lockerbie, Scotland airline bombing that killed nearly 200 Americans and dozens of Britons.

Barr applauded news that the Libyan national suspected of being the bombmaker, Abu Agila Mohammad Mas’ud Kheir Al-Marimi, was finally in U.S. custody, telling Fox News anchor Martha MacCallum in a Monday interview that the entire case is deeply personal.

"It was very personal to me, Martha, because as you say, this happened at Christmas time the month before we moved into the Justice Department as President George H.W. Bush's team there. And much of our tenure there was taken up with focus on this case, which was the biggest terrorist act against the United States up until 9/11," he said on "The Story."

"And I had to deal directly with the families. And it was an honor to engage with them. But it was searing. I felt the sadness, their grief and their desire for answers and for those responsible to be brought to justice."

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Lockerbie memorial with victims names

A man looks at the main memorial stone in memory of the victims of the bombing of Pan Am flight 103, in the garden of remembrance near Lockerbie, Scotland Friday Dec. 21, 2018.  (AP Photo/Scott Heppell, File)

Barr recounted the first Bush administration successfully capturing two conspirators in the Lockerbie bombing, adding that the Justice Department believed at the time that there was a third.

When he returned to the DOJ under Trump, Barr said the feds gleaned leads on Mas'ud and were able to pursue his capture.

Barr later said the evidence collected in the case spanned many miles of Scottish countryside, including a piece of what was later discovered to be a portable cassette player that the bomb had been housed in.

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Libyan man charged in Lockerbie bombing

This image provided by the Alexandria, Va., Sheriff's Office shows Abu Agila Mohammad Mas’ud Kheir Al-Marimi, who is in custody at the Alexandria Adult Detention Center, Dec. 12, 2022 in Alexandria, Va.  (Alexandria Sheriff's Office via AP)

"There were over 4 million little scraps of evidence spread over this area and the FBI and other U.S. agencies and certainly the Scottish police did an outstanding job of investigation," he said, calling the crime scene the largest in history.

Twenty-five miles from the site of the bombing, the discovery of a piece of circuit board no larger than a fingernail helped ultimately crack the case, the former top lawman added.

The suspect later found himself in custody of Libyan authorities after the fall of strongman Moammar Qaddafi, where he claimed to have been involved in the bombing, Barr said.

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"That information got to the United States in 2016. And the [DOJ] followed up on this information and confirmed a lot of the information. And by the time at the end of the Trump administration, we felt confident enough to pursue charges against him. He was in Libyan custody at the time."

A DOJ statement from earlier Monday gave no information on how Mas'ud came to be in U.S. custody.

In 2001, former Libyan intelligence officer Abdelbaset al-Megrahi was convicted of bombing the flight. He is to date the only person convicted over the attack. He lost one appeal and abandoned another before being freed in 2009 on compassionate grounds because he was terminally ill with cancer.

Fox News' David Spunt and Danielle Wallace contributed to this report.