In an afternoon address President Barack Obama said the world is appalled by the murder of American journalist James Foley at the hands of ISIS but vowed to stay firm in efforts against the terrorist group.
"We will be vigilant and we will be relentless," Obama said.
"Jim taken from us in an act of violence that shook the conscience of the entire world," he said. "Today, the American people will all say a prayer for those who loved Jim. All of us feel the ache of his absence. All of us mourn his loss."
ISIS released a brutal video on YouTube of the apparent murder late Tuesday, saying Foley's death is in retaliation for U.S. airstrikes in Iraq. They're sending a warning to President Obama and America.
The chilling video appears to show the 40-year-old American photojournalist on his knees with his executioner next to him, holding a knife in his left hand.
Foley was a seasoned foreign correspondent on assignment for the GlobalPost when he disappeared in northern Syria in November 2012.
Robert George, a member of the U.S. Commission on International Religious Freedom, joined the petition. He spoke more about this effort, on The 700 Club Wednesday.
Sign the Petition for the United States and International Community to Defeat ISIS.
The terror group say his murder is retaliation for U.S. airstrikes that have stopped its advance in northern Iraq.
"This is a tragedy which is beyond imagining. There are no words to describe this kind of inhumanity," Rev. Paul Gousse, with Our Lady of the Holy Rosary and St. Leo parishes, said.
Lawmakers in Washington say ISIS is capable of carrying out an attack on U.S. soil and warn that the president must deal with the terrorists now.
"I mean, ISIS method of diplomacy are beheadings, crucifixions, mass executions or live burials, and enslavement of women and forced marriages. These are evil people that need to be defeated," Sen. Ron Johnson, R-Wis., said.
Islam: Religion of Peace or War?
Arabic scholars bring you a historical and shocking narrative on the tenets of Islam and the life of its founder.
Know the truth. Download now.
Around the globe, vocal opposition to ISIS is growing. In Germany, thousands of Kurds, Yazidis, and others took to the streets of Hannover, calling on the the international community to intervene.
Religious leaders are speaking out, too. On Monday, the Pope gave his blessing to efforts to stop the terrorist group.
Patriarchs in Lebanon are also calling for for action to stop the persecution of Christians displaced in Iraq.
Even Muslim leaders are slamming the actions of ISIS. Saudi Arabia's top cleric said the group is Islam's No. 1 enemy. Representatives of several Muslim organizations call the radical group a "monster."
Meanwhile, a group of religious scholars in the United States are calling for the destruction of ISIS.
The online petition, signed by Rev. Russell Moore, with the Southern Baptist Convention, and others, says "none of us glorifies war but warns that nothing less can stop the Islamic militants' campaign of genocide against religious minorities and unconscionable acts of barbarism against defenseless women and children."
ISIS is threatening to behead another American hostage if the United States keeps up its airstrikes. Steven Sotloff, who worked as a freelancer for Time and other news organizations, was kidnapped near the Syria-Turkish border just over a year ago.
Meanwhile, Foley's mother paid tribute to her son on Facebook.
"He gave his life trying to expose the world to the suffering of the Syrian people," she wrote. "Like Jim, they are innocents they have no control over American government policy in Iraq, Syria or anywhere in the world."