The videos of Steven Sotloff and James Foley were released within a two-week period by ISIS
Foley, a freelancer working for the Agence-France-Presse and GlobalPost, went missing in Northern Syria in November 2012. His beheading is the first murder of an American citizen by ISIS since the conflict in Syria broke out in March 2011.
Sotloff disappeared in August 2013 while reporting from Syria. He was a freelancer for publications including Time and Foreign Policy.
More than 80 journalists have been kidnapped in Syria since the civil war began and 68 journalists have been killed with seven murdered this year including Sotloff and Foley.
There have been 124 American airstrikes on ISIS targets since August 7.
"Just as your missiles continue to strike our people, our knife will continue to strike the necks of your people" stated an ISIS militant figure before beheading Sotloff.