The wife of Cooper University Health System chief executive John P. Sheridan Jr. died from a stab wound to her chest that punctured her aorta, officials said Tuesday.

Nearly five months after the couple's deaths, authorities disclosed Joyce Sheridan's cause of death, but a final determination of the cause and manner of death for her husband has not been issued by the New Jersey Office of the State Medical Examiner.

Joyce Sheridan's death was ruled a homicide shortly after the couple's deaths Sept. 28, public records have indicated, but officials had declined to reveal what caused the 69-year-old woman's death.

The Sheridans were found unresponsive amid an intentionally set fire in the master bedroom of their home in the Skillman section of Montgomery Township, Somerset County. Sources have said John Sheridan, 72, also had stab wounds.

The unexplained deaths have fueled a mystery in New Jersey political circles. John Sheridan was a former state transportation commissioner who worked on transition teams for Gov. Christie and Gov. Christie Whitman.

While authorities have not yet concluded the case, the Sheridans' four sons - Mark, Matt, Dan, and Tim - were briefed by the Somerset County Prosecutor's Office several weeks ago, a relative said.

Joyce Sheridan's brother, Peter Mitchko, 72, said he was told by a representative of the Prosecutor's Office that the sons, along with two attorneys, met recently with officials at the office to discuss the investigation. Mitchko, who has publicly demanded answers about his sister's death, said he was not told the status of the probe.

Somerset County Prosecutor Geoffrey D. Soriano, whose office is leading the investigation, has released few details. In a letter to The Inquirer last week, he wrote that "among other things, we await a determination of the cause and manner of the death of John Sheridan" by the medical examiner.

Soriano's letter, in response to inquiries from the newspaper, said the criminal investigation continues. The state Attorney General's Office and New Jersey State Police are also a part of the investigation.

Paul Loriquet, a spokesman for the Attorney General's Office, said state police were notified of the deaths within hours of the fire. Acting Attorney General John J. Hoffman was informed shortly afterward.

Loriquet said that Hoffman, the top law enforcement officer in the state, is notified of any "major incident" or cases involving prominent people.

Sources with knowledge of the case have said investigators initially theorized the deaths were a murder-suicide. Regarding such suspicions, Loriquet said, "It would have been premature to make any conclusions at that time."

Although Loriquet disclosed Joyce Sheridan's fatal chest wound, he declined to comment Tuesday on any other injuries, or the cause and manner of John Sheridan's death.

"The medical examiner's office has not issued a final report on [John Sheridan's] autopsy," Loriquet said. "That's what's holding everything up."

The Medical Examiner's Office has referred questions about the deaths to the Attorney General's Office, which oversees medical examiners.

Early in the investigation, the Sheridan family hired Michael Baden, a nationally known forensic pathologist, to examine the deaths. Baden declined to discuss the case Tuesday.

Mitchko, who spoke with Baden weeks after his sister and brother-in-law died, said he was told Baden discovered a wound on John Sheridan's neck that nicked his jugular vein. The wound was not noted in the New Jersey medical examiner's initial report, but the examiner later concurred with Baden's finding, Mitchko said.

Mitchko said that Baden reported carbon monoxide was found in John Sheridan's blood. Two knives from the home were recovered, Mitchko said, but wounds on John Sheridan were believed to have been made by a weapon or weapons not recovered, raising the specter of a missing weapon. Officials have not addressed those details.

Sources with knowledge of the investigation, who have requested anonymity, have also said that John Sheridan was found under an armoire and that a gas can, normally kept in the garage, was recovered at the scene. Joyce Sheridan had numerous knife wounds to her upper body, sources said.

John Sheridan was pronounced dead at the scene. Joyce Sheridan, a retired teacher, was declared dead a short time later after being transported to a hospital.

One of the couple's sons, Matt, was arrested by Montgomery Township police that afternoon on drug possession and paraphernalia charges. Authorities said cocaine, baggies, and a scale were found in his car. The Prosecutor's Office has said that the arrest was unrelated to the deaths and that authorities have not pursued the charges.

The Prosecutor's Office has also said the couple's sons "played no role" in the deaths and that there was no threat to the public.

The Sheridan sons declined comment Tuesday night. "They're not going to have anything to say until the prosecutor issues a formal finding and concludes his investigation," said Tom Wilson, a family spokesman.

Mark Sheridan, general counsel for the New Jersey Republican State Committee, is the administrator for his parents' estate, with an estimated value of $2 million. A will has not been located, according to a lawyer hired by the family to assist with the estate.

The state's top officials, including Christie, have also remained quiet on the case.

Michael Drewniak, a Christie spokesman, wrote in an e-mail last month that "the governor does not speculate or get involved in investigations in any way. He didn't like it when politicians did it when he was U.S. attorney, and he won't do it now as governor. Investigations are all different, some more complex than others, and we will leave public comments to the investigators."

bboyer@phillynews.com

856-779-3838 @BBBoyer