The man who committed a triple murder in Marrero placed dolls and toys around his young sons’ bodies to create a macabre, staged scene before killing himself Sunday morning, the Jefferson Parish coroner said Monday.

Dr. Gerry Cvitanovich said investigators believe David Mata, 46, killed his wife Kelli, 40, and their sons Liam and Caden, 2 and 4, by slicing their necks inside the family’s home in the 4800 block of Brandi Street in Marrero. Mata had several stab wounds himself, Cvitanovich said, but authorities suspect he ultimately died of an overdose.

The coroner’s assessment of the bloody murder-suicide came as friends and acquaintances expressed shock that Mata could have slain his wife of three years and their two children.

There had been at least one warning sign, however: Mata cut Kelli, then his girlfriend, in the face with a glass vase when she was 8½ months pregnant with one of their children, according to a 2010 police report.

Cvitanovich said the bathrooms and kitchen in the Matas’ well-kept house were clean. Inside the boys’ separate rooms, both Caden and Liam were lying in their beds with blankets pulled up to their necks — and both of those necks had been sliced once.

“He had laid toys and dolls around the boys,” Cvitanovich said. “It was staged.”

Closer to the front door, said Jefferson Parish Sheriff’s Office spokesman Col. John Fortunato, the boys’ parents were found together in a pool of blood.

Cvitanovich said Kelli Mata had a skull fracture and a single slice wound to the neck, which suggested that she had first been hit on the head and then killed. Investigators found no defensive wounds on her during an autopsy.

David Mata, meanwhile, was lying at a right angle to his wife, with his head resting on her torso. He had several non-lethal, self-inflicted stab wounds. But Cvitanovich said his office believes the man actually died of an overdose. Investigators found several prescription bottles in the house, but he declined to name the drugs.

The murder-suicide scene was discovered by Kelli Mata’s 18-year-old daughter from a previous marriage, deputies said.

Shawn LeBlanc, the girl’s father and Kelli Mata’s ex-husband, said he has had several run-ins with David Mata. He declined to describe them.

“We’ve had our issues with him. Threatening issues,” LeBlanc said. “He did have a past.”

Even so, LeBlanc said, the call he got on Sunday — telling him that his ex-wife was dead — was a shock.

LeBlanc’s daughter had just returned from a camping trip with him when she discovered the adult couple’s bodies. He said the first thought that raced through his head was what would have happened if his daughter, too, had been inside the house.

“I never expected to deal with this. This is shocking,” LeBlanc said. “I kind of just want to wake up and have this be a bad dream. The survivors are going to suffer for the rest of their lives.”

Fortunato said detectives have yet to establish a motive for Mata’s actions. No one had called 911 from the Marrero house in the roughly six months the couple had lived there, he said.

However, deputies were called to the Matas’ previous residence in the 4300 block of Jean Lafitte Boulevard in Lafitte, according to a police report. Deputy Michael Leyva wrote that when he was dispatched to the house about 6 p.m. on July 26, 2010, a very pregnant Kelli Mata narrated a disturbing chain of events.

Kelli Mata, at the time known as Kelli Fabre, told the deputy that David Mata was “drinking and destroying the house.” The incident began when he came home after having a few drinks and cursed at the daughter from a previous marriage. Mata refused to leave the house, picked up a remote control and threw it toward Kelli, shattering a glass vase.

Mata then picked up a glass shard and threw it at Kelli’s face, causing a minor cut to her left cheek, she said. She continued to tell him to leave the house. But David Mata refused to leave, she said, and at one point charged at her body, though she was 8½ months pregnant with his child.

David Mata was booked and pleaded guilty to domestic abuse battery that year.

The Matas’ next-door neighbor in Lafitte, 83-year-old Vincent Wiseman, said he remembered well when deputies came to arrest David. Kelli Mata was his brother-in-law’s stepdaughter, and she grew up in their tight-knit community in Lafitte.

He was familiar with David Mata from neighborhood crawfish boils, he said. But the news he heard Sunday afternoon took him totally aback.

“How do you kill two little kids like that?” Wiseman asked. “No, I don’t know too much of what went on in their house.”