Relatives of former Cooper University Health System CEO John P. Sheridan Jr. and his wife, Joyce, on Friday took their criticism of the investigation of the high-profile couple's deaths to national TV.

One of their sons, Mark, and John Sheridan's brother, Peter, appeared on Good Morning America to denounce the probe.

The two were found dead after a September fire at their Somerset County, N.J., home. Prosecutors said last week that their investigation determined that John Sheridan fatally stabbed his wife, set the fire in their bedroom, and took his own life.

"We're not going to allow the Prosecutor's Office to destroy my father's legacy, my mother's legacy, to protect them from their screw-ups," Mark Sheridan said in the recorded interview.

The family said prosecutors were hasty in their investigation, jumping too quickly to the conclusion that John Sheridan killed his wife and himself.

"They assumed it was a murder-suicide the second they walked on the scene," Mark Sheridan said on the broadcast.

Peter Sheridan said prosecutors had "indicted and convicted my brother when there hasn't even been a trial."

The family says many questions about the deaths at the Sheridans' Montgomery Township home remain unanswered.

"The community should be scared," Mark Sheridan said on GMA. "The prosecutor had no idea what happened at that crime scene and he was out telling the public they were safe."

The interview was not the first time the family has condemned the investigation.

In a statement last week, the couple's sons called the prosecutor's findings "nothing more than an expedient way" for the office to "put an end to its embarrassing bungling of this murder investigation."

A lawsuit challenging the prosecutor's findings is likely, an expectation reiterated on GMA.

"We will not allow our father to be convicted based on guesswork resulting from an inadequate and incomplete investigation simply because he is not here to defend himself," the sons said last week.

The Prosecutor's Office declined to comment to GMA, citing the threat of litigation.

Officials have not offered a definite motive for John Sheridan's alleged actions, but said he was "out of character" and "very upset" in the days before the deaths.

On the day of the deaths, John Sheridan had been scheduled to meet with Cooper staff to discuss a report expected to be critical of the hospital's mortality rates for coronary artery bypass graft surgeries.

The Prosecutor's Office released its findings after months of secrecy surrounding the case.

Even before last week's announcement, a bitter fight had been unfolding between the Sheridan family and investigators. The family, disagreeing with how some aspects of the case were handled, hired a nationally known forensic pathologist to examine the deaths.

Prosecutors said Joyce Sheridan was stabbed in the head and chest, and had defensive cut wounds on her hands. John Sheridan died from sharp-force injuries and smoke inhalation, prosecutors said, and was alive after the blaze was set.

Prosecutors said they did not find the knife or sharp weapon they determined John Sheridan used on himself, but noted a 2- by 6.5-inch piece of metal was found embedded in the floor near his body.