Who Is Abu al Umarayn? ISIS Leader Held Responsible for 2014 Death of Former U.S. Army Ranger, Killed in Drone Strike

A senior ISIS leader said to be involved in the 2014 killing of a former U.S. Army Ranger, was killed Sunday in a drone strike over Syria, according to the U.S.-led coalition.

Abu al Umarayn, along with "several other ISIS members" were killed in Syria's Badiyah Desert by drone strikes, coalition spokesperson Col. Sean Ryan said in a statement.

"Al Umarayn had given indications of posing an imminent threat to Coalition Forces and he was involved in the killing of American Citizen and former U.S. Army Ranger, Peter Kassig," officials said in a statement, according to a Fox News report. "He has been linked to and directly involved with executing several other prisoners as a senior ISIS member."

"Coalition airstrikes continue to disrupt ISIS command and control on the battlefield as we remove key figures from their ranks," the statement continued.

Kassig, 26, was taken as hostage in Oct. 2013 while on a humanitarian trip to Syria with Special Emergency Response and Assistance, an organization he founded in 2012.

The Indiana-native, a converted Muslim, was going by the name Abdul Rahman Kassig at the time of his kidnapping.

A video posted online documented the aftermath of Kassig's death. Though the act was not recorded, a masked man with a decapitated head at his feet, said: "This is Peter Edward Kassig, a U.S. citizen."

"Peter, who fought against the Muslims in Iraq while serving as a soldier under the American army, doesn't have much to say. His previous cellmates have already spoken on his behalf," the masked militant continued.

In the month prior to Kassig's brutal death, his mother Paula Kassig sent out a series of tweet pleading for her son's safety.

"We have tried to contact you directly to plea for the life of our only son, Abdul Rahman Kassig, and have not received any response," she tweeted. "Please tell us what more we can do so that Abdul Raman may continue to serve and live his life in accordance with the teachings of Islam."

Parents of Abdul Rahman Kassig Request Instruction from the Islamic State pic.twitter.com/7auWNPa5t4

— Paula Kassig (@PaulaKassig) October 23, 2014