Peter Kassig first visited Beirut on a college spring break trip. What the former Army Ranger saw there prompted him to return, the next time as a medical assistant and humanitarian worker hoping to offer blankets, food and medical care to victims of the region's conflicts.

Kassig founded a nongovernmental organization that provided aid for refugees fleeing the civil war in neighboring Syria. But his work in Lebanon led to his capture by militants on Oct. 1, 2013, while en route to eastern Syria.

On Friday, Kassig, 26, appeared in an online video that purported to show a masked militant who threatened to behead the Army veteran next, after the apparent beheading of British hostage Alan Henning.

The Associated Press could not immediately verify the video's authenticity, though it was released in the same manner as other Islamic State group videos and the masked militant sounded similar to the one who carried out other slayings.

In a statement issued Friday evening, National Security Council spokeswoman Caitlin Hayden confirmed that Kassig was being held by Islamic State militants.

"At this point we have no reason to doubt the authenticity of the video released earlier today. We will continue to use every tool at our disposal — military, diplomatic, law enforcement and intelligence — to try to bring Peter home to his family," Hayden said.

The video and threat were a heartbreaking development for Kassig's family and friends, who have stayed silent since his capture while working to secure his release.

Kassig's parents issued a statement Friday describing their son's work and asking for privacy.

"We ask everyone around the world to pray for the Henning family, for our son, and for the release of all innocent people being held hostage in the Middle East and around the globe," the statement said.

According to his parents, Kassig, an Indianapolis native, converted to Islam while in captivity and now goes by the name Abdul-Rahman.

In a January 2013 interview with Time, Kassig said he traveled heavily throughout Lebanon to assess the needs of people there.

He said he designed his aid organization, Special Emergency Response and Assistance, or SERA, around a belief that "there was a lot of room for improvement in terms of how humanitarian organizations interact with and cooperate with the populations that they serve."

SERA, he said, focused on supplementing the work of larger organizations by delivering aid that could "do the most good for the most people over the longest period of time possible."

"It's about showing people that we care, that someone is looking out for those who might be overlooked or who have slipped through the cracks in the system for whatever reason," he said.

SERA has since suspended its efforts while Kassig's family has worked to win his release.