In one of his last acts as attorney general, Bill Barr announced new charges against an alleged top bomb maker the U.S. claims is responsible for the 1988 bombing of Pan Am flight 103 over Lockerbie, Scotland, on the 32nd anniversary of the attack.

“Let there be no mistake: no amount of time or distance will stop the United States, and its partners in Scotland, from pursuing justice in this case,” Barr said at a press conference unsealing a criminal complaint against Abu Agila Mohammad Masud on Monday.

Masud is charged with destruction of an aircraft resulting in death and destruction of a vehicle of interstate commerce by means of an explosive resulting in death. The U.S. is now seeking his extradition to the U.S. from Libya, where he has been serving a separate ten-year sentence for bomb making.

The charges could lead to the first U.S. trial stemming from the attack, and on Monday, Barr deemed the prospect of bringing Masud here to face justice as “very good.”

Officials Monday explained that the complaint is largely based on a confession Masud had made to Libyan authorities in 2012, as well as his travel records, which tie him to the crime. Scottish authorities received the information in 2017.

On December 21, 1988, Pan Am flight 103 was in the air after departing London en route to New York when a suitcase bomb put on the plane detonated over Lockerbie, killing 270 people, including 190 Americans. Among them were 35 students from Syracuse University, returning to the country after spending a semester studying abroad.

“We have always been assured that this was an open case and no lead would be unfollowed. Today is the culmination of that hard work, said Kara Weipz, who spoke on behalf of the families of the victims at the news conference. She added, “We will continue to pursue justice for all who were responsible for this bombing. But today is a small victory in that conquest.”

In 1991, during his first stint as attorney general, it was Barr who announced charges against two Libyan officials, Abdel Basset Ali al-Megrahi and Lamen Khalifa Fhimah in connection with the bombing.

The Scottish government also brought charges against the men, and in 2000 a trial was held at Kamp van Zeist in the Netherlands, considered a neutral location for the proceedings, where ultimately Megrahi was convicted and Fhimah was acquitted in 2001.

Megrahi was released early from prison in 2009 and died three years later. Barr said Monday that the Scottish government has also not ruled out bringing charges against Masud.

“This investigation is by no means over,” Barr said at the 1991 press conference. “It continues unabated. We will not rest until all those responsible are brought to justice. We have no higher priority.”

On Monday, Barr described the case as having been “unfinished business” and called his announcement of the charges a “full circle” moment. Last week Barr informed the president that he would be resigning before the holidays and is set to depart the Justice Department on Wednesday.

The evidence investigators linked to Megrahi in 1991 included unaccompanied baggage they say originated in Malta. On Monday officials say that travel records indicate Masud traveled to from Tripoli to Malta prior to the bombing and allege that is when he created the explosive device.

Masud also admitted in his confession to being the bomb maker behind the 1986 attack on the LaBelle Discotheque in Berlin, West Germany that killed two American service members and one Turkish woman.

“To the families of those who died in the sky above Lockerbie all those years ago, I know that the small step we take today cannot compensate for the sorrow you feel to this day,” Barr said Monday. “But I hope that you will find some measure of solace in knowing that we in the United States Government, on behalf of the American people and in partnership with our counterparts in Scotland, have never relented, and will never relent, in the pursuit of justice for you and your loved ones.”

Paulina Smolinski contributed to this report.