A Railway Protection Force (RPF) constable on Monday shot dead four persons on board a running train near Palghar railway station in Maharashtra, an official said.
Constable Chetan Kumar Choudhary fired from his automatic weapon, killing an RPF Assistant Sub-Inspector (ASI) and three other passengers of the Jaipur-Mumbai Central Express shortly after 5 am, the official said.
According to a senior police official, the accused RPF constable was mentally unstable.
Palghar is around 100 km from Mumbai.
The constable opened fire on his escort duty in-charge ASI Tika Ram Meena in the running train, the official said.
After killing his senior, the constable went to another bogie and shot dead three passengers, the official added.
The accused then tried to escape from the train between Mira Road and Dahisar, but was later nabbed by the Government Railway Police (GRP) personnel and his weapon was also seized, he said.
The accused is in the custody of the Mira Road railway police, the official said.
The bodies were taken out of the train at Borivali railway station, he said.