Raymond Yellowknee (right), shown here in Dec. 2007, died early Thursday morning. ((CBC))

A man who was serving 16 years in prison for killing a northern Alberta mother and her three daughters while driving drunk has died in an apparent suicide at Edmonton Institution, the Correctional Service of Canada said Thursday.

Police and the chief medical examiner's office have been called in to investigate the death of Raymond Yellowknee, 37, as is the practice when someone dies in custody. 

Yellowknee was sentenced in June 2008 for the deaths of Misty Chalifoux, 28, and her daughters Michelle, 13, Trista, 9 and Larissa, 6.

At that time, a Crown application to have Yellowknee designated a dangerous offender was turned down by a judge in Slave Lake, Alta. Had it been successful, he would have been first person in Canada to be given that designation for chronic drunk driving.

However, the judge ruled while Yellowknee met most of the statutory requirements for dangerous offender status, evidence showed Yellowknee was not a psychopath and could be treated for his alcoholism.

The judge designated Yellowknee a long-term offender and sentenced him to 20½ years in prison. Yellowknee was given credit of 4½ years for time he had already spent in custody.

In January 2006, Yellowknee was drunk and driving a stolen truck near Slave Lake, Alta. when, chased by the RCMP, he swerved across the highway and smashed head-on into the car driven by Chalifoux. 

Chalifoux was taking her daughters on a shopping trip to Wal-Mart.

Yellowknee was convicted of four counts of impaired driving causing death along with evading police and driving while his licence was suspended.