A man who was struck by a train and killed in Sydney's south overnight was believed to have been running across the railway tracks after vandalising another stationary train, police say.
The 25-year-old man was hit by the passenger train near Kingsgrove Railway Station just after midnight.
Police and paramedics arrived at the station a short time later but could not revive the man, who died at the scene.
A NSW Police spokesman said an investigation into the circumstances surrounding the man's death was ongoing.
Initial inquiries, however, suggested the man may have just vandalised another stationary train before he ran across the train tracks and was struck.
It is believed he did not see the south-bound passenger train that hit him. That train was carrying scores of passengers from the city towards Macarthur at the time.
All south-bound trains between Turrella and Macarthur on the T2 Airport Line were suspended while officers from the St George Local Area Command established a crime scene, which was examined by forensic officers overnight.
Passengers had to remain on the train for more than an hour after the collision, before they climbed from their carriages onto the tracks and were put on to buses to continue their journeys.
Police said the man who died had not been formally identified on Monday morning.
The T2 line reopened about 3.30am on Monday, and Sydney Trains said services had since returned to normal.
Police will prepare a report for the coroner.