According to 9 News, a police search involving the dog unit and Polair took place in a desperate attempt to find the unnamed child after he ran from the institution in Oatley Parade in Sydney's south at approximately 7.15pm.
Authorities revealed the boy had been found dead at Oatley Train Station just before 9.30pm. He's said to have been hit by a train.
The news outlet also reports that the deceased was known to have had mental health issues.
As a result, trains were delayed due to the tragic fatality.
A thorough investigation is currently underway into the circumstances surrounding the child’s death, and police are appealing to anyone with information to contact St George Police or Crime Stoppers on 1800 333 000.