First an explanation video, and then the only copy of the scenes from the show we could find that hadn't been deleted from YouTube.
Here's more from the YouTube description:
A scene depicting runners at the Boston Marathon being killed and another depicting two bombs being detonated are SEPARATE SCENES but they are in the SAME EPISODE.This episode of Family Guy was broadcast 3 weeks ago.The media is labeling this whole issue a "hoax" and Seth McFarlane is calling anyone who talks about it "abhorrent," when he's the guy who made a cartoon making light of killing Boston Marathon runners and detonating bombs.Hollywood Reporter article admits they are from the same episode. "Turban Cowboy," which premiered in the U.S. on March 17, culminates with a scene depicting Peter Griffin accidentally blowing up a bridge by dialing a terrorist's cell phone. But in the video making the rounds online, the cell phone scene is placed immediately after an unrelated moment in the episode when Bob Costas, voicing himself, asks Peter how he won the Boston Marathon."