This is the second part of a two-part series. The first part can be found here.
Mark Sheridan knew from the second he walked into his parents’ Skillman, New Jersey, home that something was awry.
Just days earlier, at the end of September 2014, his parents — beloved teacher Joyce Sheridan, 69, and her 73-year-old husband, Republican politico John Sheridan — were discovered repeatedly stabbed inside their bedroom, which had then been set on fire with the couple barricaded inside.
One of the weapons used in the stabbing was nowhere to be found. And a fire poker was inside the room even though they have no fireplace upstairs.
"The evidence we do have strongly suggests it was a double homicide rather than a murder suicide"
Blood riddled the lower railing of the steps to the second floor and blood splatter marked the top of the staircase. And investigators said the splatter was consistent with an attack being carried out at the top of the stairs.
Yet, authorities decided within three days that they were done processing the crime scene, raising eyebrows — and concerns — among grieving loved ones who sought answers.
Nearly eight years later, they’re still waiting.
Joyce and John Sheridan had four sons and created a "very close," "very active" family, one of their adult children, Mark Sheridan, told Fox News Digital.
"My parents were always around," he said. "My father worked in a lot of big jobs and in important roles. And yet, he always made time and was at sporting events … They made it work."
He described how his mother was "really the one in charge," while his father was her "easygoing" counterpart.
"She was the commander-in-chief for the most part — managed to keep us all in line as much as she possibly could," he said with a laugh. "My father was the cool, calm, collected one. My mother was the more fiery one, the more troublesome one. She liked to joke. She liked to prank. She gave it as good as she got."
Joyce Sheridan was a teacher for more than 15 years before retiring, at which point she "devoted much time to her grandchildren" and on her hobbies, which included knitting and gardening, according to an obituary for the couple.
Prior to his death, John Sheridan served as president and CEO of Cooper University Health Care in Camden, New Jersey.
He had previously spent years in state government, including working with former New Jersey Gov. Chris Christie’s transition team, serving as a commissioner for the New Jersey Department of Transportation, general counsel for the New Jersey Turnpike Authority and deputy attorney general for the state of New Jersey, according to the obituary and reports.
The family – Joyce, John, most of their sons, in-laws and their grandchildren – got together at the couple’s home just weeks before the tragedy on September 7, 2014, for John’s birthday, Mark recalled.
"[We] had a nice meal, spent the day with my parents. They were playing with my children, having fun. It was a normal family get-together for dad's birthday," he recalled. "Probably four or five hours at the house having dinner and spending time together."
He talked to them sporadically throughout the next month and spoke with his mother that week, he added.
"The last real, meaningful interaction I had with them was on September 7 for his birthday."
On Friday, Sheridan described how it was "really hard to remain encouraged" despite the circumstances and the passing time.
"Candidly, we've accepted the fact this will likely remain unsolved absent a confession," he continued. "We doubt there will ever be a resolution. Too many mistakes were made during the most important time of the investigation.
"Our only hope at this point is that there is a confession."
The Sheridans' deaths have since become the topic of public and media scrutiny and have become the subject a local WNYC Studios podcast exploring the circumstances.
'TOO MANY MISTAKES'
When asked if he had ever questioned whether the Somerset County Prosecutor's Office's version of events was accurate, Mark Sheridan responded, "We have never said that this couldn't be a murder-suicide."
"Instead, we maintain that there is insufficient evidence to reach that conclusion. All the evidence we do have strongly suggests it was a double homicide rather than a murder suicide," Sheridan added.
Sheridan's parents were found dead on a Sunday. By the Wednesday, the family grew suspicious, he said.
Just one day prior, a Somerset County law enforcement official described the crime scene to the family during a meeting, only for them to arrive at the home on Wednesday to find nothing made sense.
"We became suspicious [of] the investigation on the Wednesday after they died. At that point, we were given possession of the house," Sheridan wrote in an email Friday. Their fears were confirmed, he said, when the state medical examiner and a family-hired forensic pathologist, the famed Dr. Michael Baden, agreed that "they did not have the knife used to kill my father."
The lifeless bodies of longtime teacher Joyce Sheridan and her Republican politico husband John Patrick Sheridan Jr. were discovered in the bedroom of their home in the early morning hours of Sept. 28, 2014.
Police and firefighters received a call just before 6:15 a.m. for a report of a fire at the couple’s Somerset County home. They arrived to find the fire had erupted only in an upstairs bedroom, where officers discovered John and Joyce unresponsive inside.
John was pronounced dead, and Joyce was rushed to an area hospital but could not be saved.
The case was initially ruled a murder-suicide, with Somerset County investigators announcing that John Sheridan killed his wife by stabbing her in the chest before stabbing and killing himself.
Assistant Medical Examiner Dr. Eddy Jean Lilavois performed autopsies on both Joyce and John Sheridan. Lilavois determined that Joyce was stabbed multiple times and ultimately died from a "stab wound of chest perforating aorta." He classified the manner of her death as "homicide."
Meanwhile, John had suffered at least five stab wounds. The cause and manner of his death were initially listed as "pending further studies" and "pending investigation," respectively. Lilavois later determined John Sheridan died from suicide as a result of "sharp force injuries and smoke inhalation."
But in the absence of the weapon used in John Sheridan’s death – which even Lilavois allegedly acknowledged – and with a second opinion from Dr. Baden, officials ultimately changed course and listed the manner of Mr. Sheridan’s death as "undetermined."
Asked what he saw as being the most glaringly suspicious details surrounding the case, Sheridan pointed to the missing weapon, the fire poker and one of his father's injuries, which police allegedly did not acknowledge.
"[M]y father had five broken ribs and straight lines bruises across his chest, yet the police ignored a four-foot-long wrought iron fire poker found in their bedroom," he wrote. "The bedroom doesn't have a fireplace. The poker came from the downstairs.
"Finally, every expert you [have] examine the blood spatter outside the bedroom agrees that is (sic) is cast off from a stabbing that occurred at the very top of the stairs right outside the bedroom."
After years of public criticism from the Sheridans’ adult children over the way the case was handled, a spokesperson for the Attorney General’s office revealed in May that the office was investigating the matter and would "follow the evidence wherever it leads."
Mark Sheridan received a phone call from the attorney general’s office around April or May, around the time that the office had opened the investigation, but he has not heard from anyone since.
Spokesperson Steven Barnes wrote in an email earlier this month that the investigation "is ongoing, and no further information is being released at this time."
A spokesperson for the Somerset County Prosecutor's Office referred all inquiries to the Office of the State Attorney General in response to a Fox News Digital request earlier this month.