Joseph Eaton was charged with killing his parents, their two family friends, and shooting into cars on a highway in April (Picture: AP)

A man who confessed to shooting and killing his parents and two of their friends was charged with stealing nine guns after their murders.

On April 18, the bodies of David Eaton, 66, Cynthia Eaton, 62, Robert Eger, 72, and Patti Eger, 62, were found inside a home in Bowdoin, Maine. All four were killed by gunshot wounds, police said.

According to an affidavit, the Egers owned the home in Bowdoin, but were letting the Eatons stay at the property while they waited for their son to get home after being released from prison.

Shortly after the bodies were found, police in the nearby town of Yarmouth responded to reports of a shooter firing on cars on Interstate-295 – just 20 miles from the gruesome crime scene.

Investigators search the home where four people were found dead in Bowdoin, Maine (Picture: AP)

One 911 caller told dispatchers they saw a ‘suspicious male’ standing at a highway exit, ‘standing in the middle of the road waving his hands with what appeared to be blood on him.’

Three members of a family were injured on I-295, who were later identified as Sean Halsey, 51, Justin Halsey, 29, and Paige Halsey, 25.

Joseph Eaton, 34, was arrested after police scrambled to the scene in Yarmouth. According to investigators, he confessed to killing his parents and the Egers while in police custody.

Eaton was indicted by two different grand juries in Sagadahoc County and Cumberland County on a total of 27 charges, which include murder, firearm theft, and attempted murder.

Eaton is also facing attempted murder charges for firing at the Halsey family, as well as three more motorists on the highway.

Additionally, Eaton was charged with aggravated animal cruelty for killing the Egers’ dog – a golden doodle named Max.

He was also charged with stealing a large amount of weapons and between $1,000 and $10,000 from his parents and the Egers after their deaths.

According to investigators, Eaton stole eight guns owned by Robert Eger, and a ninth firearm owned by his mother, Cynthia Eaton.

It is unclear if the guns Eaton used for the murders and highway shootings were the same ones he stole. He was legally prohibited from owning firearms after serving prison time for aggravated assault.

Investigators are still searching for a motive for the massacre.

One investigator at the crime scene in Bowdoin found ‘a note on the kitchen island that stated someone had been molested and that there was nothing done about it,’ according to the affidavit. ‘The note also mentioned being freed of pain and the writer of the note wanted a new life,’ the document reads.

The note was not signed or attributed to anyone, the affidavit states.

Eaton has not yet been arraigned on the charges and has not officially entered a plea.

According to investigators, Joseph Eaton confessed to killing his parents and the their friends while in police custody.