A man who was serving life in prison for the murder of his parents and two family friends has died in a Massachusetts prison.

Joseph Eaton, 36, died Tuesday morning, according to a press release from the Maine Department of Corrections.

The Massachusetts Department of Corrections said in a statement that a person, who the department did not identify, died at the Souza-Baranowski Correctional Center in Lancaster, Massachusetts, after suffering a medical emergency around 4:15 a.m. Tuesday.

The Worcester County district attorney’s office confirmed that the person who died in custody was Eaton.

Eaton’s cause and manner of death have not yet been determined, a spokesperson for the Massachusetts medical examiner’s office said. Preliminary findings indicate there was “no foul play involved,” according to the Massachusetts Department of Corrections.

The Massachusetts State Police is investigating Eaton’s death, the Maine Department of Corrections said in its press release.

Eaton was sentenced to life in prison last year after pleading guilty to fatally shooting his parents, Cynthia and David Eaton, as well as family friends Bob and Patti Eger at the Egers’ home in Bowdoin in April 2023.

The morning after the shooting in the Bowdoin home, Eaton opened fire on several cars on Interstate 295. Three people were shot and injured. Eaton later said he mistook the cars for police officers he thought were pursuing him.

Eaton told the Press Herald in a series of interviews in 2023 that his troubled life led up to a “psychotic break” during the shootings.

Eaton’s attorney, Andrew Wright, said in a statement Wednesday that he was sad to hear he had died.

“Joe never knew why he did what he did,” Wright said in the statement. “What he was full of was remorse, the reason he took responsibility for his actions. He killed those who loved him most. However, he was a father, and a human being and this is a very tragic ending for a tragic life.”

Before Eaton’s death, The Boston Globe reported that four people had died in the Massachusetts prison system in just over a month, including someone being held in the same facility where Eaton was housed. All had reportedly suffered medical emergencies and don’t appear to be connected, The Globe reported.

Eaton was brought to the facility in Massachusetts through the Interstate Corrections Compact, according to the press release from the Maine Department of Corrections. Under the interstate compact provision, out-of-state prisons must regularly update the Maine Department of Corrections about the person in custody, according to Maine law.