Federal jurors signaled Thursday they are struggling to reach a verdict in the trial of one of two men accused of killing four people during last year's hijacking of the "Joe Cool" fishing charter boat.

On their third day of deliberations, the 12 jurors sent a note to U.S. District Judge Paul Huck asking if 20-year-old Guillermo Zarabozo was "automatically" guilty of a crime if he brought a gun aboard, even if he didn't know something bad would happen.

Zarabozo testified that he brought a 9mm Glock handgun in his luggage but blamed the killings on 36-year-old Kirby Archer, who has pleaded guilty in the case. Zarabozo testified he was unaware that Archer planned to commandeer the boat and that Archer shot all four victims using Zarabozo's weapon.

Under that scenario, Zarabozo should not be convicted for simply carrying the gun aboard, his lawyers said.

"The answer to that question is clearly no," said defense attorney Anthony Natale.

Prosecutor Karen Gilbert, however, said the question was vague urged Huck to direct the jurors to consider his legal instructions carefully to find the answer. The judge decided to do just that, and jurors ended deliberations a short time later. They are to return Monday.

Zarabozo, a security guard from Hialeah, faces life in prison if convicted of murder, conspiracy, kidnapping, robbery and using a firearm to commit a violent crime in the hijacking of the 47-foot "Joe Cool" on Sept. 22, 2007.

The boat's captain, his wife and two crew members were killed aboard the vessel and their bodies tossed into the ocean. They were never found, nor were any murder weapons.

The boat was discovered out of fuel and drifting far south of its original destination in Bimini, Bahamas, with Zarabozo and Archer found a few miles away in the boat's life raft. They initially told the Coast Guard and FBI a tale about being attacked by Cuban pirates, but both later admitted that was untrue.

Prosecutors say they were trying to make it to Cuba, where Archer could hide from child sexual molestation and theft charges in Arkansas.

Zarabozo testified that he was told only that they were going on a lucrative security job in Bimini and that it might lead to other work with CIA connections Archer claimed to have. Archer is a former Army policeman but did no security or intelligence work, prosecutors said.