What should the US response to James Foley execution be ?

ISIS has murdered the American journalist James Foley, and has another journalist in their custody. Just before Mr. Foley is murdered he is presumably forced to say some very personal anti American things. The ISIS terrorist speaking with a British accent makes some threats against the US, says this murder is revenge for the air campaign recently launched in Iraq, and then cuts James Foley's head off. So what do you think the US response should be, what do you think Obama should do? Please participate in this poll.