Prosecutors: Man killed Marshfield couple in their 70s, locked dog inside oven

BROCKTON − He's accused of brutally killing a Marshfield couple in their own home and suffocating their pet dog, but prosecutors provided no clear answers as to why 28-year-old Christopher Keeley would have committed the crimes at a superior court arraignment this week.

Keeley, of Weymouth, went before a judge in Brockton on Tuesday to face two counts of murder and additional charges of animal cruelty, car theft and fraudulent use of a credit card. He was indicted on the charges by a Plymouth County grand jury earlier this year and has been in jail since his district court arraignment in December.

Keeley, represented by Attorney Thomas Iovieno, pleaded not guilty on all charges. He was ordered held without bail at Tuesday's hearing, where a dozen family members of the victims watched on. Keeley is due back in court in Plymouth on June 29.

Police say Keeley killed Carl and Vicki Mattson, both 70, inside their Marshfield home just after Thanksgiving. He is also accused of killing the family dog by locking it inside the oven.

Assistant District Attorney Amanda Fowle told the court that Keeley knew the Marshfield couple because he was friends with their adult son, who now lives in Arizona. Keeley lived with the Mattsons "for some time" in the fall of 2022, Fowle said, but had since moved out.

It was a fight with friends on Thanksgiving Day that pushed Keeley to Marshfield, Fowle said. The Weymouth woman with whom he was staying asked him to leave following the argument, and friends drove Keeley to the home at 75 Gotham Dr. His friends dropped him off and later told police Keeley "was indicating that if things in his life didn't change, he might hurt or seriously kill someone," Fowle said.

The prosecutor said it sounded like Keeley snuck into the Mattson home on the evening of the 24th and into an upstairs bathroom. The couple was arguing downstairs about their dog's barking, which led Carl up the stairs to check on the dog. He found Keeley, and a physical fight followed. Carl Mattson was found dead at the bottom of the stairs.

"There is no further information as to how Mrs. Mattson became involved in the struggle, but she was found in a room near the struggle," Fowle said. "There was a knife sticking out of her neck at the time she was found."

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Friends told police they heard from Keeley briefly via Facebook the next day, when he sent a message saying there was a "1% chance" the Mattsons were still alive. Surveillance footage shows Keeley met with friends that day at the Quincy Walmart parking lot while driving the couple's Jeep, Fowle said, and video shows he may have had help cleaning out the car.

"The defendant himself, his clothing and his boots were covered in what appears to be blood," Fowle said "He was brought a change of clothes so he could change." He spent the next few days staying with friends and used the Mattson's credit card at a bank in Weymouth and to buy a bus ticket out of state, Fowle said.

Other friends who could not get in touch with Keeley called Marshfield police on the 26th requesting a wellbeing check on him at the Gotham Drive address. The home appeared empty, the car was gone, nobody answered the door, and nothing was amiss outside, police said. Officers were able to contact a family member of the Mattsons, who said Keeley no longer lived there, so police left the home.

On Nov. 29, a wellbeing check was called in for the Mattsons at the same address and police returned, entered through the front door and found both bodies.

"The knife is discovered, the amount of blood is found, and the investigation starts in earnest at that time," Fowle said, adding that Keeley's palm print was lifted from the knife.

Later, when crime scene technicians returned to continue processing the scene and start cleaning up, they found the body of the family dog inside the oven. A necropsy determined it had died from lack of oxygen.

Keeley, who was 27 at the time, took a bus from South Station in Boston to Georgia and later to Florida. He was arrested in Miami Beach on Dec. 2. He appeared before a judge in the Florida 11th Circuit Court via Zoom and agreed to be brought back to Massachusetts to stand trial.

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At the time of the slayings, Cruz said Keeley had "prior involvement" with the court system and that mental health issues could be at play.

A search of Quincy District Court records showed five cases that have gone through the system in the past decade, including charges of assault, malicious destruction of property and breaking and entering. Court documents revealed a lengthy rap sheet that started when Keeley − for whom court records show addresses in Quincy and Weymouth − was 18.

Reach Mary Whitfill at mwhitfill@patriotledger.com.

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This article originally appeared on The Patriot Ledger: Accused killer in Marshfield Mattson murders arraigned in Brockton