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A school teacher accused of killing his wife while on a luxurious Mexican cruise allegedly told investigators that he killed his wife "with his bare hands," according to court documents filed late Friday.

Robert John McGill, 55, of Los Angeles, "stated he killed his wife in the bathroom of their cabin with his bare hands," FBI Special Agent James B. Stinnett wrote in a probable cause affidavit. The document was attached to a criminal complaint charging McGill with one count of murder in the death of his wife, Shirley McGill.

Stinnett also wrote that McGill was informed of his Miranda rights and he replied that he understood those rights and was willing to answer questions without the presence of an attorney.

Calls to McGill's attorney were not immediately returned. At his court appearance earlier in the day, she declined to comment on the case.

U.S. District Magistrate William McCurine Jr. entered a plea of not guilty on McGill's behalf, as is common practice in federal court at initial appearances.

McGill was distraught during the brief hearing and argued with federal public defenders about whether he could make a statement to the court as his family members sobbed in the gallery. He appeared without handcuffs and wore a white jumpsuit.

"They're suffering now," McGill was heard saying as he gestured to his family. "I don't think it is for the best. I think they are suffering and need to hear from me."

"That's putting more financial burden on top of the pain and horror that I've caused this family," he added before the hearing resumed.

It wasn't immediately clear to what McGill was referring.

McGill's family, including two adult sons, declined to comment after the hearing, as did Assistant U.S. Attorney Joanna Curtis.

McGill is charged with killing his wife on Tuesday, which was also his 55th birthday, as the Carnival Elation cruise ship steamed home after a stop in Cabo San Lucas, Mexico.

Shirley McGill turned 55 just six days before she died. The San Diego County medical examiner's office said she died of strangulation and blunt force injury to the head and torso.

Stinnett noted in the court papers that Robert McGill's knuckles "appeared as if he had been in a fight."

The death was reported to Carnival crew members around 8:20 p.m., but authorities have placed the time of Shirley McGill's death about two hours before, according to the court documents. Robert McGill was not in the room when the body was found, but was taken into custody by ship security later on, authorities said.

He was placed in the brig and about 20 FBI agents intercepted the ship on a U.S. Coast Guard cutter late Wednesday and interviewed McGill and more than 50 witnesses while the Elation was still at sea.

Friends and neighbors said they were shocked to learn of the charge. They said the pair seemed to be living a romance story: ex-high school sweethearts who found each other decades later and renewed their love.

"It doesn't make any sense. You are talking about a situation that just doesn't have any connection to the people I know as neighbors," said Michael Hougardy, who lives on the McGills' cul-de-sac in the San Fernando Valley area of Los Angeles.

"Bob and Shirley never said anything negative about each other," he told The Associated Press on Friday. "I saw Bob a couple days before they left. He was excited. He was looking forward to it."

The first sign of trouble came on Tuesday, three days into the five-night cruise, when a passenger contacted ship security to express concerns that a woman might be dead, said Keith Slotter, a special agent in charge of the FBI's San Diego bureau.

McGill was a divorced father of two sons when he reconnected with Shirley through the Internet, colleagues said.

Court records show McGill was divorced from his first wife in 1998 after a 2 1/2-year proceeding and then filed for bankruptcy in 2001. Two years later, he married Shirley McGill in Las Vegas.

In bankruptcy papers, McGill listed assets of $50,000 to $100,000 and debts of $100,000 to $500,000. The attorney who handled the case did not immediately return a call seeking comment.

"Bob and Shirley loved each other very much. Their marriage was the most important thing in his life," Paul White, a teacher at the school where McGill taught, told the AP. "They were childhood sweethearts."

White said he worked with McGill for nearly 11 years and knew him to be calm and pleasant.

"He's a great friend, he's great with kids, he's a great dad, he's a great husband," White said.

McGill, whose gray hair falls below his shoulders, played guitar, liked to ride horses and hike and "was always out every morning walking the dogs," Hougardy said.

McGill has worked for the Los Angeles County Office of Education since 1979 but would likely be placed on administrative leave if his case is prosecuted, spokeswoman Margo Minecki said.

Colleagues said McGill spent years teaching at-risk teens, became burned out by the job a decade ago but was revitalized when he came to work at the West Valley Leadership Academy in Canoga Park, a county-run alternative high school that White founded to help at-risk youth. The county closed it in June because of dwindling attendance.

McGill had switched teaching jobs a few years ago and was tutoring pregnant teenagers in an independent-study program.

Mo Freedman, who worked with McGill at the county education agency for 20 years, called him "a free thinker" who enjoyed his work.

"We all get a little cynical at one time," Freedman said. "I thought Bob was like that years ago, and then he reacquainted with his high school sweetheart, Shirley. He was reinvigorated. And Paul (White) kind of pulled him out of the doldrums, working with the kids."

Shirley McGill retired last week from the state Department of Motor Vehicles, and her husband had planned to retire soon as well, acquaintances said.

Hougardy said Shirley McGill planned to move to Oregon, where her family and her children from a previous marriage lived. McGill was going to join her when he retired.

A detention hearing in the case is set for July 23, with a preliminary hearing on July 30.

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