A militant organizer wanted in connection with the controversial 2012 attack on the U.S. diplomatic facility in Benghazi, Libya, was captured and is being sent to the United States, the White House said Monday.

Mustafa al-Imam was apprehended Sunday in Libya and "will face justice for his alleged role" in the attacks that killed four U.S. officials, President Trump said in a statement.

"To the families of these fallen heroes: I want you to know that your loved ones are not forgotten, and they will never be forgotten," Trump said. "Our memory is deep and our reach is long, and we will not rest in our efforts to find and bring the perpetrators of the heinous attacks in Benghazi to justice."

Al-Imam was arrested during a special operations forces raid in Libya, the Associated Press reported. He was captured just before midnight local time Sunday and is expected to be in the United States within the next two days.

The Sept. 11, 2012, mortar attack killed four Americans, including Ambassador Chris Stevens, and was investigated by Congress to determine if there was any misinformation given to the public by the Obama administration and then-Secretary of State Hillary Clinton. Three other U.S. officials, Glen Doherty, Sean Smith, and Tyrone Woods, were also killed.

Stevens was the first U.S. ambassador killed in the line of duty since 1979. State Department officials were later criticized for not providing more security at the consulate prior to the attacks.

The Benghazi probe also brought to light Clinton's use of a private email server to conduct government work. The ensuing firestorm and criticism of the use of the private email server drew intense media and political scrutiny in the weeks before the 2016 presidential election.

"The United States will continue to support our Libyan partners to ensure that ISIS (the Islamic State) and other terrorist groups do not use Libya as a safe haven for attacks against United States citizens or interests, Libyans, and others," Trump said. "Libya’s long-term stability and security are linked to its ability to form a unified government and military."

United States Secretary of State Rex W. Tillerson said the investigation into the attack has persevered to find the people responsible. He also said he has been in contact with some of the victims' family members "to underscore the U.S. government's unwavering support."