Israel has confirmed that slain American journalist Steven Sotloff was also an Israeli citizen, while President Barack Obama vowed to build a coalition to "degrade and destroy" the extremist group that carried out the videotaped beheading.
Sotloff's Jewish faith and Israeli citizenship were not widely known before his death in part because Israel's military censor apparently kept a lid on the story for his safety and his killers may not have known about his background either, since they made no mention of Jews or Israel in the footage released Tuesday.
Sotloff, a 31-year-old from suburban Miami who freelanced for Time and Foreign Policy magazines before he was captured in Syria a year ago, became the second American newsman to be beheaded by Islamic State militants in two weeks, killed in retribution for US airstrikes against the group.
The video horrified Americans and journalists around the world and touched a nerve in Israel, where news that Sotloff had connections to the country dominated newscasts and brought condolences from Israelis who knew the Miami-area native.
"Steve was part of a group of young Jewish Americans who are enamored with Israel and enamored with the Arab world," said Ehud Yaari, an Arab affairs commentator for Israeli Channel 2 who met Sotloff. "They were dying to know and enter all the dangerous places, and that's how he behaved."
The killing also put pressure on the Obama administration to act more forcefully against the extremist group that has conquered a swath of Syria and Iraq.
"Our objective is clear, and that is to degrade and destroy ISIL so that it's no longer a threat," Obama said during a visit to Estonia, using an acronym for the group.
"We will not be intimidated. Their horrific acts only unite us as a country and stiffen our resolve to take the fight against these terrorists," the president said. "And those who make the mistake of harming Americans will learn that we will not forget, and that our reach is long and that justice will be served."
During an appearance in Maine, Vice President Joe Biden declared that the US will pursue the militants to "the gates of hell."
Obama also sought to clean up the political damage inflicted when he said last week that "we don't have a strategy yet" for dealing with the Islamic State.
"It is very important from my perspective that when we send our pilots in to do a job, that we know that this is a mission that's going to work, that we're very clear on what our objectives are, what our targets are," the president said.