US man kills wife on cruise ship because she 'would not stop laughing'

A cruise ship passenger accused of killing his wife of two decades did it because "she would not stop laughing" at him, a witness says.

US man Kenneth Manzares, 39, was arrested on murder charges after he was caught trying to drag Kristy Manzares' body to the balcony of their cabin off the coast of Alaska.

Court documents say a passenger on board the boat arrived to the blood-splattered scene and pulled the body back into the cabin, and waited until medical workers and security officers arrived.

When the witness asked Manzanares what happened, he says Manzares replied: "She would not stop laughing at me."

Friends told CBS News the Utah couple were high school sweethearts, and they were celebrating an anniversary.

Passengers on board the Emerald Princess, which was carrying 3,400 passengers and 1,100 crew members on a weeklong trip, say the couple was on board with a large group, including their three children.

Kristy Manzares, a real-estate agent, died from a "severe head wound", court documents say - but the official cause of death is not known.

The FBI is investigating.