Carrington Michael Costa, 26, of Florida, died of multiple gunshot wounds to the head, according to the Snohomish County Medical Examiner's Office. His death was ruled a homicide.
His grandmother, Shirley Irene Champagne, 70, died from a close-range gunshot wound to the head. Her death has been ruled a suicide, the medical examiner's office said.
Both were found dead at the Champagnes' mobile home in Marysville on July 6.
Shirley Champagne's husband, 82, had called 911 about 9 a.m. to report finding the bodies in the living room at their home in the Glenwood Mobile Estates park in the 5900 block of 64th Street NE.
The Marysville police investigation is ongoing, Lt. Darin Rasmussen said Friday.
Detectives are waiting on laboratory test results to confirm what they believe happened, he said.
Court records from Florida show that Costa had a history of mental health problems. His family there had called police on him for being violent with them as recently as June.
Before moving to Marysville, Costa had been living along the Gulf Coast in the Pensacola area, about an hour southwest of Mobile, Ala.
He had recently moved to Washington to live with his grandparents, Marysville police said.
Costa was arrested in Florida on June 4 after repeatedly hitting his stepfather, according to the arrest report from the Santa Rosa (Fla.) County Sheriff's Office.
Costa's mother told police that he had called Shirley Champagne and threatened to burn his mother's house down.
His mother also told police that Costa was diagnosed with bipolar disorder in his late teens. She said that he sometimes stopped taking his medication. His counselor had terminated their sessions about a year before because Costa threatened him, his mother told Florida police.
Marysville police said last week that they believe Costa may have been off his medication at the time of his death.
Costa moved around the country frequently and struggled to find employment, police records show. Relatives, including Shirley Champagne, had given him places to stay in various cities but would become overwhelmed with his behaviors, according to police reports.
Costa pleaded guilty June 26 to misdemeanor domestic-violence-related battery in connection with his June 4 arrest in Florida.
The Santa Rosa County Sheriff's Office also was called for a family disturbance involving Costa in 2006, police records show.
Shirley Champagne then was living in the area, and she and Costa had an argument, police wrote in the report. She told police she didn't want Costa at her home anymore.
Washington state Department of Revenue records show that the Champagnes purchased the Marysville mobile home in July 2011.
Neighbors at Glenwood Mobile Estates last week said Shirley Champagne recently had gone to Florida to bring back her grandson after he got into some kind of trouble there.
They said everyone at the park called her "Bubbles."
Rikki King: 425-339-3449; firstname.lastname@example.org
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