President Barack Obama said "the entire world is appalled" by the Islamic State's beheading of American journalist James Foley.
A highly disturbing video of the incident posted online Tuesday shows Foley kneeling next to one of the militants who is armed with a knife.
"No just God would stand for what they did yesterday or every single day," Obama said during a Wednesday press conference in Martha's Vineyard, according to ABC News. "People like this ultimately fail. They fail because the future's won by those who build and not destroy. The world is shaped by people like Jim Foley."
Foley, 40, was a freelance journalist who worked for major news outlets like the Agence France-Press in Iraq and Afghanistan, USA Today reported. He was working for the GlobalPost when he was kidnapped by armed men in northern Syria in November 2012.
U.S. officials said they tried to negotiate Foley's release by using mediators from Turkey, Russia and the Czech Republic, ABC News reported.
The Sunny jihadist group, which has terrorized civilians across northern Iraq, warned the U.S. it would execute Foley as revenge for air strikes launched against IS targets, a senior government official told the station.
IS militants, also known as the Islamic State of Iraq and the Levant, "have rampaged across cities and villages killing innocent, unarmed citizens in cowardly acts of violence," the president said.
"They abduct women and children and subject them to torture and rape and slavery...ISIL has no ideology of any value to human beings."
The identity of the masked IS fighter in the video is not clear. The U.K. believes the person is British and is attempting to identify the rebel. British officials have expressed fears that many citizens are traveling abroad to join the jihadist movements in Iraq and Syria.
After killing Foley, the IS fighter issued a threat against another American held hostage named Steven Sotloff.
Obama did not specifically mention Sotloff, who went missing in August 2013. But he said "the United States of America will continue to do what they must do to protect our people."
