Washington (CNN) A former US Marine accused of plotting a Christmas holiday terror attack on a popular San Francisco tourist destination last year was sentenced Monday to 15 years in prison.

27-year-old Everitt Aaron Jameson pleaded guilty in June after being arrested for attempting to provide material support to ISIS.

The FBI had started watching Jameson in September after finding that he "liked" or "loved" posts about terror attacks and ISIS on Facebook, according to the plea agreement.

Undercover FBI agents later posed as ISIS supporters and contacted Jameson. He met with one on December 16, and said he was well versed in the "Anarchist Cookbook," a book that includes instructions for making explosives. He also said that "we need something along the lines of New York or San Bernardino," making reference to prior terrorist attacks.

Ready to die

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