The man who in 2023 killed four people before wounding three in a highway shooting has died. 

Joseph Eaton, 36, was serving a life sentence at a Massachusetts correctional facility. 

Maine officials say he died early Wednesday morning. 

Massachusetts State Police are investigating his death. There are no other details available regarding his death, officials said.

Law enforcement officials said Eaton confessed to fatally shooting his parents, David Eaton, 66, and Cynthia Eaton, 62. Also killed were his parents’ friends Patti Eger, 62; and Eger's husband, Robert Eger, 72. Also killed was the Egers' dog. The shootings took place at the Egers' home in Bowdoin. Eaton also confessed to shooting at vehicles on Interstate 295 in Yarmouth.

The crimes took place days after Eaton was released from a Maine prison for unrelated crimes.

Authorities believe Eaton delivered the fatal shots on April 17, 2023. The victims' bodies were found the following morning, on the same day authorities say he fired at cars on I-295 in Yarmouth. 

At the time, Maine Public Safety Commissioner Michael Sauschuck called the shootings "an attack on the soul of our state." 

An unsigned note found at the scene of Eaton's killings mentioned "someone being freed of pain and that the writer of the note wanted a new life," according to a criminal affidavit. Eaton told the Portland Press Herald newspaper in jailhouse interviews that he was not in control of his actions at the time of the shootings and didn't understand why he did it.

With reporting by the Associated Press.