The mother and father of 15-year-old Ethan Crumbley face four counts of involuntary manslaughter.

Involuntary manslaughter carries a sentence of up to 15 years in prison.
Involuntary manslaughter carries a sentence of up to 15 years in prison. (AFP)

The parents of a 15-year-old boy who shot dead four students at a high school in the US state of Michigan with a gun bought for him by his father just days earlier were charged with involuntary manslaughter.

Oakland County prosecutor Karen McDonald, in a rare move by law enforcement, announced on Friday that James and Jennifer Crumbley, the parents of Ethan Crumbley, each face four counts of involuntary manslaughter.

"These charges are intended to hold the individuals who contributed to this tragedy accountable and also send the message that gun owners have a responsibility," McDonald said at a press conference.

"While the shooter was the one who entered the high school and pulled the trigger, there are other individuals who contributed to the events on November 30 and it's my intention to hold them accountable as well," she said.

Oakland County Sheriff Michael Bouchard said the whereabouts of the parents were not currently known and they were considered fugitives.

"We'll have them in custody soon," Bouchard said. "They cannot run from their part in this tragedy."

READ MORE: US teen 'shot video, discussed killing students' before shooting

Parents left town "for safety"

Shannon Smith, a lawyer, says the parents left town for their own safety but are returning to face arraignment.

In a text message, Smith says the parents have not fled from authorities. She didn't say when they would appear in court.

Four students, aged 14 to 17, were killed in the shooting at Oxford High School north of Detroit and six more were wounded, along with a teacher.

Ethan Crumbley has been charged as an adult with state murder and terror charges.

While school shootings carried out by teens occur frequently in the United States, it is unusual for parents to face charges.

James Crumbley bought the 9mm Sig Sauer semi-automatic handgun used by his son four days before the shooting.

Ethan Crumbley was with his father at the time of the purchase at a local firearms store and the teenager posted a picture of the gun on his Instagram account, writing "just got my new beauty today" along with a heart emoji.

According to police, Ethan Crumbley recorded a video on his cell phone the night before the attack saying he was planning a shooting at the school the next day, but it was not posted online.

That same day, a teacher at the school had observed Ethan Crumbley searching for ammunition on his cell phone during class and reported it to school officials.

His mother was contacted by the school but did not respond to voicemail or email messages.

McDonald said Jennifer Crumbley did exchange a text message about the incident with her son that day, writing: "lol I'm not mad at you. You have to learn not to get caught."

Involuntary manslaughter carries a sentence of up to 15 years in prison

READ MORE: Students targeted in deadly US school shooting

Source: AFP