Retired warrant officer Paul Ravensdale, 43, spoke publicly for the first time Tuesday at his sentencing hearing at CFB Shilo.
He was found guilty last month of four charges related to the death of Cpl. Josh Baker in a training accident in February 2010.
"I feel horrible and I'd like to express my deepest regrets and sorrow for the burden the Baker family has had to deal with," Ravensdale said at Tuesday's hearing.
At the time of the accident, Ravensdale was leading a test of some C-19 anti-personnel mines on a weapons range near Kandahar.
One of the mines misfired and sent hundreds of steel ball bearings flying backward, killing Baker and injuring four other soldiers.
A five-member court martial panel at CFB Shilo found Ravensdale guilty on Feb. 14 of breach of duty causing death, breach of duty causing bodily harm, unlawfully causing bodily harm and negligent performance of military duty.
He was originally charged with manslaughter but was found not guilty of that charge.
Has post-traumatic stress disorder
Ravensdale faces a maximum sentence of life in prison.
At Tuesday's sentencing hearing, Ravensdale said he has been diagnosed with post-traumatic stress disorder and depression, and he has had to seek family counselling.
"I can't move on," he told the hearing. "Every day, I re-live Feb. 12 like Groundhog Day."
The sentencing hearing heard earlier in the day from Baker's mother, Janet Baker, who had to pause several times during her testimony as she struggled to hold back tears.
"When my son took his last breath … my life was done," she said.
Josh Baker was "was very proud to be a soldier," his mother added.
Ravensdale's sentencing hearing continues on Wednesday.Suggest a correction