This is no laughing matter for Fox.
Per Reuters, a Fox rep confirmed that the episode in question, "Turban Cowboy," has been yanked from both the network's site and Hulu, and that execs have reached out to YouTube to remove the episode from its video hub.
The original episode had depicted the show's family patriarch, Peter Griffin, winning the Boston marathon, but the altered clip stitched together an unrelated scene toward the end of the episode in which the character inadvertently sets off several explosions after dialing a number on his cell phone.
Immediately after it surfaced, MacFarlane took to Twitter to condemn the hoax video.
"The edited Family Guy clip currently circulating is abhorrent," he wrote. "The event was a crime and a tragedy, and my thoughts are with the victims."
MacFarlane joins a wave of celebrities who've expressed their sorrow and support for the victims and their families, and on Monday night, talk-show hosts including Conan O'Brien and Jimmy Kimmel used their opening monologues to send well-wishes to those affected by the tragedy.