The already difficult lives of Joel and Heather Smith took a turn for the worse less than a month ago.

Joel, 33, was working multiple jobs to support his wife and their three children, and was growing more angry and depressed, said Joel’s mother, Jerys Thorpe. He had struggled all his life with depression, and Thorpe urged him to get help. It’s unclear if he did.

In a 30-minute telephone interview with the Portland Press Herald from her home in Scottsdale, Arizona, Thorpe described her son’s marriage and the young couple’s struggle to make a life for themselves in Maine, a struggle that ended in tragedy Saturday night.

Maine State Police said Joel Smith fatally shot Heather and the three children with a shotgun and then turned it on himself. Their bodies were found Sunday afternoon, after a friend, concerned that the family had not been heard from, asked a maintenance worker at the apartment complex to check on them.

For months before their deaths, the Smith family had been under financial and emotional stress, which intensified in mid-July when Joel learned that his wife was using heroin and Oxycontin, Thorpe said.

When Thorpe last spoke to her son Tuesday, he was angry at himself for not noticing his wife’s addiction sooner. He asked Thorpe to send him gas money, and she did. The family was in upheaval. Trust was breaking down. They talked seriously of leaving Maine and returning to Arizona. Joel had contacted a lawyer and was having papers drawn up seeking custody of the children, Thorpe said.

“(Joel sounded) very depressed, angry,” Thorpe said. “He just wanted his family the way it was, and it just wasn’t.”

Five days later, after grilling dinner in their apartment complex courtyard, the family was dead.

Investigators believe Joel shot his two sons, Jason Montez, 12, and Noah Montez, 7, in their separate bedrooms. Heather and their daughter, Lily, 4, were killed in the bed in the couple’s bedroom. Joel’s body was on the floor next to them, the shotgun by his side.

According to police, the quadruple murder-suicide ranks among the worst cases of domestic violence in state history. Police had no indications of prior domestic violence, and neither husband nor wife had criminal records.

After their bodies were discovered Sunday, neighbors grieved for the young family whose kids were a familiar presence around the complex.

According to police, Heather Smith told a friend that her husband had threatened suicide early last week, and pointed a gun at his head.

There was no suicide note, and police are working to determine his motivation.

Thorpe said the family had been struggling since moving to Maine from Arizona about three or four years ago, around the time the couple married.

Joel and Heather, whose maiden name is Montez, had been together for about nine years.

At the time of the wedding, Heather Montez had one son, Jason. According to Thorpe, they had two more children together, Noah and Lily.

A finish carpenter by trade, Joel also was artistic and could draw and paint, Thorpe said. Although they were unrelated, it was a trait Joel shared with Jason, who was a burgeoning artist.

“He used to tell me, ‘You know what, grandma, I just want to be an illustrator, and I can spell it, too,’ ” Thorpe recalled. “(He was) a very smart little guy, a very sweet boy.”

The parents loved their kids and doted on them, Thorpe said. In family photos from Halloween 2009, Joel, costumed in surgical scrubs with a stethoscope draped around his neck, stands with the boys, each dressed as a different comic book hero. Noah was Captain America and Jason was The Hulk.

Thorpe said Jason Montez’s biological father was not around, and Joel Smith always treated him as his own son.

When the economy in Arizona tanked around 2007 and construction work became nearly impossible to find in the following years, Joel and his new wife decided to move to Maine, where Joel’s father lived.

Earlier this year, Heather, 35, lost her job and remained out of work for nearly seven months. She only recently got a job at Portland Gastroenterology Center, Thorpe said.

Their relationship had not always been smooth, either. During earlier rough patches, Joel and Heather had sought couples counseling, and Thorpe said it made their family stronger.

But the bond of trust began to fray when Heather was hospitalized about two weeks ago, and Joel learned then that his wife was using heroin and Oxycontin, Thorpe said.

Thorpe said Joel was “kicking himself because he had not noticed it, he was unaware. They were making plans for getting rid of all their possessions and coming home (to Arizona) where they had a little better support system.”

A neighbor, Aaron Petrin, whose apartment shares a long outdoor walkway with the Smiths’ apartment, said he witnessed Heather’s apparent slip into substance abuse.

“She just recently started drinking heavily, recently maybe got into drugs,” Petrin said. “At first she was kind of the weekend warrior, partying on weekends. Then it kind of rolled over into weekdays. (Joel) was extremely against that.”

Thorpe learned of the deaths Sunday night. Another one of her sons, who was contacted by Maine authorities, called her with the news.

“He said, ‘Mom, I just got some very bad news,’ ” Thorpe recalled. “I knew before he said it. And he said, ‘Joel’s dead. All of them are.’ And then I knew.”

Thorpe said she had tried in the past to get Joel to see a therapist for his depression, which afflicted him all of his life.

” ‘You can’t do this alone, you need outside help,’ ” she remembered telling him.

“His mind was just gone, he had to be. He loved his children so much. He loved her so much. I think that’s what hurt him.”

Staff writers David Hench and Scott Dolan contributed to this report.