The parents of Peter Kassig, an American aid worker being held hostage by Islamic State militants, released a statement pleading for their son's release. (YouTube/Kassig Family)

The parents of an American aid worker taken hostage by the Islamic State released a video Saturday pleading with their son’s captors to show mercy and free the young man.

Peter Kassig’s family said he was in the region doing humanitarian work when he disappeared a year ago near the city of Raqqa in eastern Syria.

“We implore those who are holding you to show mercy and use their power to let you go,” Kassig’s mother, Paula said, while holding a picture of their 26-year-old son.

The Islamic State revealed publicly for the first time in a separate video Friday that it was holding Kassig, a former U.S. Army Ranger who served in Iraq in 2007. In the same video, a militant dubbed “Jihadi John,” beheaded an British hostage named Alan Henning, a taxi driver from Manchester. He then threatened to kill Kassig, a Muslim convert, because of U.S. bombing of Islamic State targets in Syria.

This undated photo shows former Army Ranger Peter Kassig standing in front of a truck filled with supplies for Syrian refugees. A video purportedly produced by militants in Syria released Friday shows Kassig, of Indianapolis, kneeling on the ground as a masked militant says he will be killed next by Islamic State militants. (AP Photo/Courtesy Kassig Family)

Henning was the fourth western hostage the Islamic State has executed in a series of gruesome videos. In three earlier ones, the same militant decapitated American journalists Steven Sotloff and James Foley as well as British humanitarian aid worker David Haines. The group is holding at least three other westerners, including British journalist John Cantlie and two women, one of whom is an American.

Kassig’s family said the United States’ decision to attack the Islamic State is beyond their control and more violence was a not a solution.

“We asked our government to change its actions, but like our son, we have no more control over the U.S. government than you have over the break of dawn,” Ed Kassig said. “We implore his captors to show mercy and use their power to let our son go.”

Kassig is a native of Indiana who founded SERA (Special Emergency Response and Assistance), a non-governmental organization to provide aid to Syrians fleeing the civil war in their country.

Beginning in 2012, Kassig delivered food and medical supplies and provided care to civilian casualties inside Syria, the family said.