Joel Smith shot and killed his wife, Heather, and their three children, Jason Montez, 12, Noah Montez, 7, and Lily Smith, 4, with a 12-gauge shotgun and then turned it on himself around 11:30 p.m. Saturday, police said.

Smith had no apparent history of domestic violence or abusive behavior, but had been feeling depressed and had threatened suicide, a friend told police. Police believe the 33-year-old father shot the two boys first, each in their own room on the upper floor of the family’s apartment at 35 Water St., in the RiverView apartment complex. He apparently then walked into the master bedroom and shot his wife and daughter before shooting himself. His body was found on the floor next to the bed where Heather and Lily Smith lay, the shotgun by his side.

Joel Smith used both bird shot and slugs in the pump-action shotgun, police said. They said the family members died instantly and may have been asleep.

He left no suicide note or clear indication of what may have motivated him to turn violent, state police Detective Sgt. Chris Harriman said Monday afternoon.

“There were some domestic issues, some financial problems,” Harriman said. “Until we do the rest of the interviews with the family to lock that down, we’re not sure.”

Joel Smith’s mother, Jerys Thorpe, said in an interview with the Portland Press Herald from her home in Scottsdale, Arizona, that her son had long suffered from depression and was upset to learn that his 35-year-old wife had become addicted to heroin and Oxycontin.

Thorpe said she had tried to get her son to see a therapist for his depression.

“He was also a very private person. I said, ‘It doesn’t matter who knows, you need to go (to therapy),’ ” she said. “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.”

Police are examining phone records to see if any family members made calls before the shooting Saturday night. They also are checking gun records to trace the shotgun. The couple had moved to Maine from Arizona within the past three years, and police are awaiting records from authorities there, Harriman said.

Police do not know of any protection from abuse orders or any other indications that the couple had an abusive relationship.

OUTWARDLY, A NORMAL FAMILY

Neighbors at the 60-unit RiverView complex said the family had a barbecue outside on Saturday, as they often did, and were joined by others at the complex. There were no signs of stress, and residents who live nearby said they had never heard the parents fighting.

But police said the family was experiencing financial problems.

Joel Smith worked several jobs and long hours trying to make ends meet, his mother said. In addition to working at the RiverView complex, he also did maintenance at a condominium complex in Saco and worked at Target. Heather Smith worked as a medical assistant at Portland Gastroenterology Center in Portland, according to her Facebook page. A woman who answered the business’ phone declined to comment, as did a receptionist at Phoenix Management, which operates the RiverView apartments.

A family friend became concerned about the Smiths on Sunday morning and called a maintenance worker at the complex to check on them. The worker called police around 1:24 p.m. Sunday after finding one of the bodies, police said.

Heather Lemmers, who lives next door to the family, said she knew them well. Lemmers often watched the Smiths’ children and they spent the night at her house frequently. She said her 10-year-old son was good friends with Jason and recently spent the night where Jason lived for the first time.

Her son said he had heard a noise Saturday night, but Lemmers was trying to sleep and told him to tell his father.

Lemmers spoke highly of Joel Smith, saying he jumped in the Saco River last summer to save her son when he was struggling in the water.

Lemmers thought it odd that the children weren’t out playing in front of the building Sunday morning and nobody had seen their parents.

“We were trying to figure out why they weren’t out having a cigarette, at least,” she said.

Lemmers often played with the children while their parents were drinking beer. Other neighbors in the complex said they thought Heather Smith had a substance-abuse problem, although police said there was no evidence of illegal drug use in the apartment. Police did find legitimately prescribed medicine, though Harriman would not say what kind.

Thorpe said her son and his family moved to Maine several years ago from Arizona. The family was very visible in the apartment complex, and not just because Joel Smith had started doing maintenance there within the past year.

“They were the people that were always out here barbecuing,” said Aaron Petrin, a neighbor.

A SERIES OF LOUD LATE-NIGHT BANGS

Petrin said he was sitting on the porch-like walkway Saturday night and saw the family grilling dinner. Heather Smith went inside with the children and then Joel Smith followed shortly afterward, between 8:15 and 9 p.m. Petrin said there were no signs the two had been arguing or were angry with each other.

He said he later heard what sounded like firecrackers and thought someone had lit them in the back parking lot.

Several neighbors reported hearing a series of loud bangs on Saturday night. Some attributed them to fireworks, which are set off frequently in the neighborhood. Saco Police Chief Brad Paul said others recognized the sounds as gunshots, but then assumed they were wrong.

Nobody called police, he said. Police have been called to that apartment complex many times, but never to the Smiths’ apartment.

Petrin said a stairway from the first floor led up to the Smiths’ two-floor apartment on the second and third floors. The kitchen, dining room and living room were on the second floor, and the bedrooms on the third.

The apartment complex was quiet Monday, and police were no longer at the scene. Red and white adhesive evidence tape sealed both doors into the Smiths’ apartment. A makeshift shrine of flowers, stuffed animals and the young girl’s tricycle were placed outside the complex. As rain and fog swept through in intervals, some residents sat outside smoking while others talked to reporters, expressing shock at the deaths, and bewilderment about what might have happened.

Ken Devoe, who lives in a first-floor apartment underneath the family’s apartment, said he heard no noise Saturday night. He also never heard the parents fighting.

“I heard his kids banging around, but never any arguments,” Devoe said. “They were good people.”

Heather Nason, a neighbor who baby-sat the children, is planning to hold a candlelight vigil for the family at 8 p.m. Tuesday at the RiverView complex.

Joel and Heather Smith were the biological parents of the younger two children. Jason Montez was Heather Smith’s son and Joel Smith’s stepson, police said.

Saco School Superintendent Mike Pulsifer said the Smiths’ sons attended Saco Middle School and Gov. John Fairfield School and that he met with the principals of both schools Monday.

“It’s a terrible tragedy,” he said.

Pulsifer said an email will be sent to parents to inform them about the incident and offer ways to help parents talk to their children about it.

School officials are opening Saco Middle School on Tuesday from 8:30 a.m. to 3 p.m., and school counselors will be available to talk to anyone who wishes to talk.

Detectives worked inside the family’s apartment until midnight Sunday. They interviewed some family members and friends Monday and expected to interview others arriving from Arizona later this week, police said.

The Office of the State Medical Examiner examined the bodies Monday, leading police to investigate their deaths as a murder-suicide.

NO PREVIOUS SIGNS OF VIOLENCE

Domestic violence experts say there is often a correlation between suicidal thoughts and domestic violence homicides.

“Suicidal statements should always be taken seriously,” said Julia Colpitts, executive director of the Maine Coalition to End Domestic Violence. “When domestic abuse and suicidal ideation co-exist with mental health issues, you have a toxic, potentially lethal mix that can result in homicide, as well as suicide.

“In these high-risk cases, since mother and children are experienced as a psychological extension of himself, when he ends his life, his twisted assumption is that they should die as well and not live on without him,” she said.

Besides the number of victims, Saturday’s shooting is unusual because there were few, if any, of the usual signs of ongoing abuse and control that abusers typically exhibit, police said. Previous domestic violence homicides that involved children and spouses have correlated with a breakup.

Maine Attorney General Janet Mills issued a statement about domestic violence on Monday, calling the slayings “absolutely devastating.”

“This horrific incident must serve as a reminder to all of us that threats of violence and threats of suicide must be taken seriously,” she said in her statement. “Telling your boyfriend or girlfriend ‘I can’t live without you’ can quickly cross from the innocuous to the devastating. In the context of an abusive relationship, these utterances are veiled threats of violence, with a strong undercurrent of manipulation and control. Recognizing the signs of abuse – and acting upon them – is key to preventing future tragedies like this.”

Steve McCausland, spokesman for the Maine Department of Public Safety, said this is the sixth time since 1941 that four people have been killed in a multiple homicide in Maine.

In 2006, Christian Nielsen killed four people in Newry.

In 1988, Earl Lozier shot and killed four people in Bangor, including his brother.

In 1992, Virgil Smith set fire to a building on Portland’s Munjoy Hill, where his ex-girlfriend lived, killing four people. That deadly arson was characterized as a domestic violence homicide.

In 2011, Steven Lake killed his wife, his two children and then himself at their home in Dexter.

Staff Writer Matt Byrne contributed to this report.