Fox supernatural-police drama series "Sleepy Hollow" sparked outrage on social media after it launched its "Happy Headless Day" marketing promotion Tuesday, Sept. 2 - the same day terrorist group ISIS claimed to have decapitated American journalist Steven Sotloff.

Think Jam, the PR firm charged with handling the controversial campaign, released commemorative eCards declaring Tuesday as "National Beheading Day" to promote the show's upcoming Season 1 DVD and Blu-ray release. The series was not intentionally attempting to cite the day's tragic news; instead the marketing stunt was planned to bring attention to the show's Headless Horseman character, Variety reported.

The campaign was sent to journalists by email shortly before 1:00 p.m. while news of Sotloff's beheading broke shortly after 9:00 a.m. PST, according to TV Guide.

JJ Mariani, a publicist with Think Jam, said his firm only knew the Tuesday's ISIS incident via CNN just minutes after sending out the "Headless Day" press release. The company then immediately issued a retraction and apology. Unfortunately, by that time, the eCards have already hit the web.

"We apologize for the unfortunate timing of our 'Sleepy Hollow' 'Headless Day' announcement," the firm said in a statement. "The tragic news of Steven Sotloff's death hit the Web as the email was being sent. Our deepest sympathies are with him and his family, and we don't take the news lightly. Had we have known this information prior, we would have never released the alert and realize it's in poor taste."

Fox Home Entertainment also issued the following apology: "Twentieth Century Fox Home Entertainment recognizes and apologizes for today's promotion for the Season One DVD release of Sleepy Hollow. We regret the unfortunate timing of our announcement and our deepest sympathies go out to the families of all involved."

The eCard campaign could have easily become a success if only the timing was good, Cinema Blend reported. "The eCard idea was actually a pretty cute one, featuring the 'Sleepy Hollow' characters cracking bad headless jokes. On almost any other day, these would have been shared with as many puns as possible in the article, but today is just not that day," wrote the website's Jessica Rawden.

"Sleepy Hollow" Season 1 is now available on Digital HD, while Blu-ray and DVD copies will be available Sept. 16.

"Sleepy Hollow" returns for its second season on Fox on Sept. 22.

Check out some of the "Sleepy Hollow" eCards here.