ROCKFORD, Ill. (WTVO) — Rockford was under a cloud of fog and light drizzle on Jan. 7, 1978, a slightly atypical winter day but not all that uncommon in the Midwest.

Locals were still recovering from the holiday season, taking down Christmas decorations and exchanging the last of the gifts that just didn’t work for them. It’s safe to say that for the most part, it was an ordinary Saturday for Rockford residents. Until the bodies of six children were found inside a home in the 1400 block of Camp Avenue.

It wasn’t long before Churchill’s Grove was swarmed with police cars, ambulances, news trucks, and scores of neighbors set out to confirm the mass murder in their quiet, historic neighborhood on the city’s near-west side.

Police in Milwaukee were just as quick to place 46-year-old Simon Peter Nelson in handcuffs.

Nelson would later be charged with six counts of first-degree murder in the deaths of his kids: 12-year-old Jenny, 10-year-old Simon Peter III, 8-year-old Andrew, 7-year-old Matthew, 6-year-old Roseann, and 3-year-old David. Each had been stabbed and beaten with a rubber mallet as they slept.

Nelson also killed the family dog and placed it between two of the children.

After a failed insanity defense, he took the witness stand at his trial, revealing a life of domestic violence, alcoholism, mental illness, and childhood trauma.

Nelson loved his father, he said, even though their relationship was marred by years of physical and emotional abuse. Young Simon’s weight was often the center of his father’s ridicule, prompting Nelson to refer to himself as a “fat slob” in open court.

The elder Nelson committed suicide in 1954, capping two decades of turmoil for Simon Peter, who carried it all into his first marriage.

Like his father, Nelson threatened to end his life multiple times, including once when his first wife walked out on him.

“I said if we didn’t get back together, I would kill myself,” Nelson said on the stand.

The manipulation worked for awhile, he said. But the marriage ultimately ended in 1961.

By the time he married Ann, nine years his junior, in 1964, Nelson was severely depressed, a clinical situation that continued to go untreated as the family grew.

The dysfunction mounted. Often self medicating with booze, Nelson ballooned to an unhealthy 300 pounds, performed poorly at his job, and met marital conflicts with more threats of suicide.

In one incident, believing Ann was seeing another man, Nelson put a gun to his chest but didn’t pull the trigger.

He played the victim on the witness stand, too, saying Ann threw herself completely into her job as a figure skating instructor at Riverview Ice House and neglected the family. She also took jabs at him, he said, accusing him of being homosexual.

Then came the days leading up to Jan. 7. It was a turbulent stretch as Ann planned her escape. She traveled to Milwaukee, ostensibly to clear her head and spend a few days alone.

Nelson testified that he hoped the time apart would do the marriage good. Little did he know though, Ann was done. She had already hired a divorce attorney.

When he got wind of the real reason Ann left town, Simon Peter Nelson, already a domestic abuser, became Simon Peter Nelson, the cold-blooded killer.

It is believed the massacre occurred between late Friday or early Saturday, when Nelson drove to a Milwaukee Ramada Inn, located his wife and mother of his six children, and attacked her inside her room.

As he beat her, according to Ann’s testimony, Nelson said, “They’re all dead. How do you feel?”

Tipped off by a family friend who lived in Wisconsin, police broke into the bathroom and saved Ann from becoming her husband’s seventh murder victim.

While Nelson was being taken into custody 90 miles away, Rockford cops worked what some described as the most gruesome crime scene they ever investigated.

Even today, local officials who were just kids themselves when the large man known as “Pete” to his friends turned his family home into a human slaughterhouse, are haunted by the case.

“When the name Simon Peter Nelson is raised, it conjures up the brutality and the horribleness of this unspeakable crime,” former Winnebago County State’s Attorney Joe Bruscato told WTVO in 2017.

At 15, Bruscato lived a couple blocks from Simon Peter Nelson. As state’s attorney, he fought to keep him locked up more than once.

“(My) proximity to that has left an indelible impression upon me as it’s left an indelible impression on this community,” Bruscato, now a judge, said. “This community has not forgotten.”

Simon Peter Nelson was denied parole 18 times during the 31 years he was eligible.

When Nelson first started appearing in front of the Illinois Prisoner Review Board in 1986, then-Winnebago County State’s Attorney Paul Logli launched a 20-year campaign to deny him early release.

Logli reminded the board of the horror Nelson unleashed, one that warranted every moment of his 100 to 200-year prison sentence.

Bruscato continued the fight for the next decade, often providing the panel with stacks of signed petitions and numerous reasons why Rockford’s most heinous killer should never taste freedom again.

Despite pushback from prosecutors, Nelson pleaded his case, claiming he was a changed man.

“I almost feel guilty for the fact that I’m regaining my moral compass,” he said during one hearing. “I’ve put myself back together. The remorse that I feel gets deeper the more I learn about what the weaknesses were that allowed this to happen.”

Nelson died on June 18, 2017, at St. John’s Hospital in Springfield, while in custody of the Illinois Department of Corrections. He was 85.