The Upper West Side dad believed to have stabbed his longtime love and their two young sons to death before turning the knife on himself had been “stressed” about an upcoming move to the suburbs in the days before the shocking murder-suicide.

Friends and neighbors of the “perfect” family were in disbelief Tuesday about how Edison Lopez, 41, could have fatally knifed his fiancée, Alexandra Witek, 40, and their boys, Lucian, 3, and 1-year-old Calvin, before killing himself in the West 86th Street home he grew up in.

There were “zero, absolutely zero [signs],” said Jeff Kimmel, a 22-year resident of the co-op building where Lopez worked as a super after taking over from his own father.

“I saw him evolve as an adult and as a man.”

“Everybody thought they were a great family,” another neighbor told The Post.

“They were very much a part of the community in the building.”

Although authorities have not described any motive for the killings, neighbors and police said Lopez appeared anxious over a new job in Westchester County — and the big move that would accompany it.

The apartment Lopez wanted in Hastings-on-Hudson wouldn’t be ready by their Sept. 1 move-out date, which might have caused some mental strain, NYPD Assistant Chief of Detectives Joe Kenny told reporters Tuesday.

“There may have been some problems with the timing of the relocation, meaning he had to leave his apartment on 86th Street by the 1st and we’re hearing that quite possibly the apartment in Hastings wasn’t ready for him yet,” Kenny said.

Richard Allen, a 74-year-old resident who has lived on the sixth floor since 2000, said it would have been a big upgrade from the cramped space the family of four shared.

Moreover, the building’s co-op board rejected a proposal to give his burgeoning family a larger unit because residents didn’t want to foot the bill.

“It was a step up,” Allen said.

“It was four of them in a one-bedroom apartment,” he continued.

“Would you want to do that if you could move up to a bigger job with a bigger apartment? It’s a natural thing … I talked to him about it, he was happy.”

A woman who lives in the building agreed that it “was going to afford them more space for the family,” adding that the building was about to hire a new super to replace Lopez.

“When we spoke with them about it, they seemed excited.”

But it still weighed on Lopez, according to a longtime family friend who’d lived on the block for more than three decades.

“He was upset or something … like, worried,” the man said of a Friday conversation with Lopez.

“I have never seen him like that.”

A doorman outside the family’s building also remembered seeing Lopez looking upset when he took his older son to camp on Friday.

The shocking crime has left those who knew the family grasping for answers.

Lopez and Witek met as youngsters — her dad was the doorman across the street from the West 86th Street building where Lopez’s father worked as a superintendent.

The two first-generation Americans went to high school together, then reconnected years later and had two boys.

Friends, relatives and neighbors described them as a loving family with a solid foundation.

Many of them watched Lopez, the son of Venezuelan immigrants, grow up and fall in love with Witek, whose family hailed from Poland.

“They grew up here,” said a longtime family friend, who has been a super on the same block for 35 years.

“I know him since he was a little boy and she was a little girl. I have seen them together when they were young.

“I didn’t see this coming,” he added.

“I’ve never seen [Lopez] angry, never. I’ve never seen them fighting.”

Jimmy, the block’s longtime postman, said, “[Lopez] was always nice … calm. You don’t see nothing that would lead, let’s say, trigger something like this.”

The boys were friends with other youngsters in the building, and the family had just celebrated Calvin’s first birthday a few weeks ago with a party, the resident said.

But on Monday afternoon, Lopez’s body and those of his beloved kids and childhood sweetheart were found knifed to death in their fourth-floor apartment.

When cops found their bodies, they’d been so badly mangled that officers initially thought one of them was a girl.

They found the boys in the living room with two knives lying nearby, according to police sources.

Witek lay in the hallway, a deep stab wound perforating her neck.

Her fiance was in the bedroom, perched on the bed with a sliced throat and a third knife next to him, sources said.

Cops were called when Lopez’s father and Witek’s brother — who said they hadn’t heard from the family since Sunday — drilled through the apartment lock and saw blood inside, the sources said.

“We saw them inside,” he told Gothamist, as he held back tears.

“They were already dead, whatever happened, happened maybe the day before.”

Witek — known as “Ola” to friends and family — is survived by her mother, Grace, and her brother, Lukas, according to a GoFundMe started by her grieving loved ones.

The mom of two’s murder has left her family “heartbroken and incensed,” according to the fundraiser, which had raised about $20,000 as of Tuesday night.

“A proud Polish mom, Ola shared her culture and language and made the lives of her boys bright and full,” the fundraiser said.

“Her boys loved playing with their toys, story time with mom, and were two delightful babies to all that loved them.”

In a gut-wrenching photo shared on Facebook earlier this year, Ola cradled her boys to her chest in a loving embrace.

Retired super and family friend Alfonso Barrera, 84, paid his respects Tuesday at the building’s front door, where others were starting to leave flowers and toys in the victims’ memory, and explained that his son Luis and Lopez were like brothers.

“I feel like dead. I feel like he is part of my family,” Barrera said of Lopez and his family’s deaths.

He shared a photo of Lopez smiling as best man at his son’s wedding in Arizona 11 years ago.

“He is a nice fellow, part of my family … His wife was a nice girl, beautiful girl,” he lamented before his emotions got the best of him.

Building resident Tom Holmes laid roses in four different colors on the threshold.

“One [color] for each of them,” he said sadly.

“The hopelessness … it was complete lack of hope over something, nobody seems to know,” he suggested of Lopez’s alleged actions.

“The children doesn’t deserve that nor the mother, of course … oh, my God, killing your kids, that’s the bottom.”

Patricia Roman, a hairstylist at Jeffrey Stein Salons near the family’s home, stopped by the mourning building with sunflowers and red and yellow toy cars on behalf of her co-workers.

“I work a block and a half away and I have lived here for over 20 years and just to think that that was what was going on just a few blocks away is terrible, is tragic … there is no words,” she told The Post.

She chose sunflowers, she said, in honor of Lucian and Calvin.

“They seem appropriate for children, and innocence and love and happiness,” she said.

Additional reporting by Amanda Woods

If you are struggling with suicidal thoughts or are experiencing a mental health crisis and live in New York City, you can call 1-888-NYC-WELL for free and confidential crisis counseling. If you live outside the five boroughs, you can dial the 24/7 National Suicide Prevention hotline at 988 or go to SuicidePreventionLifeline.org.