A 20 year old woman was angry because her family forced her to go on a cruise with them rather than letting her stay home with her boyfriend, so she wrote notes threatening to kill everyone on board:

The cruise ship was on a 10-day trip out of Ensenada, Mexico, when crew members found two handwritten notes on April 22 and 23, according to the charges. Both notes stated that if the ship docked in a U.S. port, the nearly 2,400 passengers and crew would all die.

After the second note was found, authorities diverted the ship to Oahu waters and a 120-member task force of federal, state and military personnel searched the ship and interviewed people on board.

The ship was searched for biological, chemical, radiological and explosive weapons, but nothing was found and the ship's cruise resumed on April 24. But Ferguson confessed the following day during an interview, Kubo said.

"The defendant said that she never wanted to go on this cruise with her family and that she wrote these notes hoping that it would shorten her time on the cruise, thereby allowing her to rejoin her boyfriend in Orange County, California," Kubo said.

Yahoo! News - Woman Charged with Cruise Ship Threat