WARNING: Audio contains distressing content 

A 17-year-old boy who threw a piece of concrete at a car in a Karawara car park, killing a pregnant woman has been sentenced to five years in detention for manslaughter and eligible for supervised release after 26 months.

Last November, Diane Miller and her family were in a car when they were caught up in a brawl at Waterford Plaza shopping centre.

The youth threw the chunk of concrete at the passenger's side, hitting Ms Miller on the head with the injuries resulting in her and her unborn child's death.

Perth Live host Oliver Peterson is outraged at the lack of "justice".