The 54-year-old refugee, from Myanmar, was travelling in the bus shuttle from the refugee campsite at West Lorengau, Ward 1, towards Lorengau town, when he jumped out the door.
Manus provincial police commander, Chief Inspector David Yapu, said the guard from Paladin Security, who was providing escort, attempted to stop him from jumping off the bus but was unsuccessful.
He said the refugee died instantly after landing to the rear left of the bus. His head was squashed after the wheels ran over him.
His body was taken to the Manus Provincial Hospital and placed in the morgue for autopsy.
The incident occurred at about 10.45am today.
PPC Yapu said the motive of his death is not known but it is a suicide case.
He said so far, there are three suicide cases involving refugees reported in Manus Province, including the latest one.
Police are investigating the incident, stated Yapu.