Donna Delbono told police “my son’s killed someone” after he stabbed a teen to death over a £20 debt.
Joshua Delbono, 19, knifed 16-year-old Charley Bates through the heart during a fight in Radstock, Somerset, last July.
In an interview with the Daily Mail, his mum Donna explained why she made the decision to shop him to the authorities.
She said: “I didn’t for a second, consider not reporting Josh. It didn’t enter my head to try to protect him.
“But as I picked up the phone I felt sick. I was shaking, crying. I didn’t know how to say what I needed to say.
“It absolutely broke my heart to make that call but I had no alternative. I made the right decision and I’d do it again in the same circumstances.”
Donna added that her son wept as she made the call, but she was determined to see justice done for his victim.
She explained: “In just three minutes a young man’s life ended and Josh’s life changed forever.
“I remember shouting at him, ‘What in God’s name was going through your head?’ I had no idea he had a knife. I’ve never known him to carry one. That’s why it shocked me so much.
“I felt so terrible for Charley’s mother. I couldn’t face his parents. I told Josh I wanted to support him but I couldn’t.
“I felt such pain for Josh but that was nothing compared with Charley’s mother’s pain.”
Joshua Delbono was sentenced to life in prison with a minimum term of 21 years after being convicted of murder.
The killing is believed to have come about over a debt owed by his victim to one of his pals.
A fight was sparked when Joshua’s group of friends confronted Charley, during which he grabbed a knife and stabbed the youngster.
Donna added that he is “not coping well” in prison and claimed that he has been on suicide watch.
She said: “He has really bad dreams, flashbacks from the scene. He talks about his guilt and feels terrible remorse.
“He’s working hard — first he had a job in the laundry, then he was cleaning toilets, then a job in the kitchen. He calls me two or three times a day.
“I know Josh is full of remorse and regret. He will be feeling for Charley’s mother without a doubt.
“Do I hope she’ll forgive him? I’d like to hope that one day she just might. But I think that would be just too much to ask of her.”