Police investigate after 3yo boy found dead in Sydney, man in critical condition

A three-year-old boy is dead and a man is in a critical condition after an incident at a unit in Sydney's south today.

Police were called to a complex at Riverwood about 4pm.

The child was found dead inside. 

A 45-year-old man with serious injuries was located at the scene, and he was taken to hospital in a critical condition, according to police. 

A crime scene has been established.

More to come.