ISIS has released a video that it says shows the beheading of American journalist Steven Sotloff.  

An internet video posted today purports to show the beading of Sotloff by the militant group.

He hadn't been seen in Syria since August of last year -- until he appeared in a video released last month by the Islamic State group that showed the beheading of fellow American journalist James Foley.

In the video, the fighter who appears to behead Sotloff says, "I'm back, Obama" -- and says it's because of an "arrogant foreign policy toward the Islamic State." The fighter says, "Just as your missiles continue to strike our people, our knife will continue to strike the necks of your people."

His mother released a video last week pleading for her son's release. 

At the end of the video, he threatens to kill a third captive, a British man -- David Haines.

A White House spokesman said he wasn't in a position to confirm the authenticity of the video, and added, "Our thoughts and prayers first and foremost" are with Sotloff's family.

If confirmed, this would be the second U.S. journalist beheaded in the past two weeks. Reporter James Foley was executed on Aug. 19. 

Stay tuned to NewsRadio KFBK and KFBK.com for updates on this developing story. The Associated Press contributed to this report.