Attorney General Merrick Garland struck a solemn tone in remarks at the Oklahoma City memorial Monday morning as he recognized the lives lost in the bombing of the Alfred P. Murrah Federal Building 26 years ago, while drawing a parallel to the domestic terror threat currently facing the homeland.

"Although many years have passed, the terror perpetrated by people like Timothy McVeigh is still with us," Garland said. "Just last month, the FBI warned of the ongoing and heightened threat posed by domestic violent extremists. Those of us who were in Oklahoma City in April 1995 do not need any warning."

Garland, who will sit later Monday with ABC News Chief Justice Correspondent Pierre Thomas for the first exclusive interview of his tenure as attorney general, played a major role in the investigation and prosecution that brought McVeigh and his co-conspirator Terry Nichols to justice.

One of Garland's first acts upon landing in the state, he noted, was successfully arguing before a magistrate judge that McVeigh should remain behind bars pending their continued investigation. Following his conviction, McVeigh was put to death in 2001 -- while Nichols continues to serve out his life sentence in federal prison without the possibility of parole.

Choking back tears as he described his experience arriving at the scene of the explosion two days after the truck bombing, Garland said an "army of first responders" were combing through the wreckage searching for survivors, and "everyone was crying."

"At the time, we did not know exactly how many people had died," Garland said. "But we did know that the children's center, which had been at the front of the building, was gone. Then and there, we made a vow. We promised that we would find the perpetrators, that we would bring them to justice, and that we would do so in a way that honored the Constitution."

With roughly a thousand in attendance at the memorial ceremony due to restrictions from the COVID-19 pandemic, Garland made a point to thank those in the community who he said had graciously welcomed and cared for his team of investigators in the months that they were in the city investigating the attack.

"We tried to treat you as we would have wanted our own families to be treated," Garland said. "And in return, you and all of Oklahoma City treated us like family. You took care of us – the first responders, investigators and prosecutors who had converged on the city from across the country."

MORE: In return to Justice Department, Garland brings background in domestic terror to a nation in crisis

Garland stressed to the audience that amid a heightened threat from domestic extremists his department continues to work to ensure that a tragedy like the one that struck Oklahoma City 26 years ago will not happen again. In his confirmation hearing in March, Garland noted his experience handling the Oklahoma City bombing and other domestic terror cases as he promised to aggressively prosecute those involved in the assault against the U.S. Capitol on Jan. 6.

"The Department of Justice is pouring its resources into stopping domestic violent extremists before they can attack, prosecuting those who do, and battling the spread of the kind of hate that leads to tragedies like the one we mark here today," Garland said Monday. "We must all stand together against them -- for the safety of our communities and for the good of our country."

He used his speech at the ceremony Monday to reflect on his experienceworking alongside the Justice Department, FBI and state and local officials to build their vast criminal case following one of the deadliest acts of homegrown terrorism in U.S. history.

McVeigh, a Gulf War veteran motivated by anti-government and racial hatred, detonated a rental truck packed with explosives in front of the building the morning of April 19, 1995, killing 168 people and injuring hundreds more. He was arrested roughly 90 minutes after the attack by a state trooper who stopped him for driving a vehicle without a license plate.

Alexander Mallin, ABC News, April 19, 2021

Voices4America Post Script. 1921 Tulsa Race Massacre, 1995 OKC Bombing, 2021 January 6 attack on the Capitol - #MerrickGarland, our Attorney General, describes them as of one piece - all designed by white supremacists. He will prosecute. Get ready! A great and empathic man. #JOEsAG