Washington (CNN) US forces captured Mustafa al-Imam in Libya for his alleged role in the 2012 Benghazi attacks that killed four Americans, including Ambassador Christopher Stevens, the White House announced on Monday.

"Yesterday, on my orders, United States forces captured Mustafa al-Imam in Libya," President Donald 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."

Mustafa al Imam may have operated under different aliases, an administration official told CNN. The US government has video of al Imam present at one of the two sites of the attacks that killed four Americans, the official said. It's not initially clear whether the video shows al Imam at the consulate or the annex which was also attacked.

The official said the US had been monitoring the terrorist operative's location for some time.

Once Al Imam was captured, he was flown to a US Navy ship, the official said. Al Imam will be transferred to the US for federal prosecution but it is unclear at this time when that transfer will take place.

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