A man who told police he killed his parents and their friends and shot at motorists on a busy interstate highway might try to show he was insane, based on pleas he entered Friday.

The 34-year-old ex-convict Joseph Eaton entered pleas of both not guilty and not criminally responsible, leaving him the option of an insanity defense against charges including four counts of murder.

"At this point we are preserving the ability to move forward with the so-called insanity defense. Once we have more forensic information, full discovery, and are able to view the case as a whole, we will then decide how to proceed," Andrew Wright, one of his attorneys, told The Associated Press before the hearing in West Bath.

MAINE MAN INDICTED, ACCUSED OF KILLING PARENTS AND 2 OTHERS

Law enforcement officials say Eaton confessed to the killings at a property in rural Bowdoin, and to wounding three people while shooting at vehicles on Interstate 295 in Yarmouth.

Eaton has been jailed since his arrest on April 18 near the chaotic scene along the highway, where traffic backed up as heavily armed law enforcement searched the area.

MAINE POLICE IDENTIFY GUNMAN WHO ALLEGEDLY SHOT AND KILLED FOUR PEOPLE, WOUNDED THREE OTHERS

The bodies were found in Bowdoin that morning, days after Eaton’s mother picked him up at a prison in Maine where he had done time for violating probation on an aggravated assault conviction, the latest in a long criminal history.

Eaton’s parents, Cynthia Eaton, 62, and David Eaton, 66, were killed along with their longtime friends, Bowdoin homeowners Robert Eger, 72, and Patti Eger, 62, officials said. Also killed was the family dog, resulting in a cruelty to animal charge. He was also charged with stealing weapons.

Police still don’t know Eaton’s motive for the slayings. A criminal affidavit stated that an unsigned note found at the scene mentioned "someone being freed of pain and that the writer of the note wanted a new life."