The boys were both 14. And both their mothers shed tears in court yesterday as the devastating impact of the tragedy on their families was detailed at a sentencing hearing for the teenage shooter.

The boy, who cannot be named for legal reasons, pleaded guilty to the manslaughter of his friend. He was originally charged with murder.

He and his friend Josef were alone at his family's Orangeville property last December when a motorist sought their help after his car broke down. The boys were afraid and armed themselves, defence barrister Richard Pontello told Campbelltown Children's Court.

The boy took a pump-action shotgun from his father's wardrobe. Trying to determine whether it was loaded, he pulled the trigger and shot Josef, who was two metres away. Mr Pontello said it was ''a split-second lapse in proper judgment'', with tragic consequences.

The boy suffered post-traumatic stress and was profoundly remorseful. He missed his mate tremendously, Mr Pontello said.

The teen used to be happy, friendly and outgoing. Since the shooting he kept to his room and was quiet and withdrawn. ''I have to live with this forever,'' he told a cousin.

His mother told the court the boy was ''just sad all the time''. ''He's lost his friend and he feels terrible about it,'' she said.

Weeping in the witness box, she described finding suicide notes while snooping in her son's bedroom. He had written ''that he was sorry that this happened and his friend had gone''.

Her husband, 41, is serving periodic detention after pleading guilty to several firearms offences, including possessing an unregistered shotgun and failing to keep the weapon safely.

The woman told the court she tended to blame him ''for doing this to us''.

Josef's mother, Rosemary Ferraro, made a victim impact statement to the court, saying she thought he was in a safe environment at his mate's house.