Singh is presently lodged in Thane Central Prison after being remanded into 14 days’ judicial custody on August 11.
Singh was part of an escorting team on the train on July 31, with three other RPF personnel.
According to the GRP, he had an argument with his senior, ASI Tikaram Meena, about not being relieved from duty despite his ill health.
Singh is accused of gunning down ASI Meena from point-blank range in coach B5. About half an hour later, he shot down an elderly passenger, Kadar Bhanpurwala, at another location in the same coach. He then moved to coach B2, where he took a passenger, Syed Saifuddin, hostage at gunpoint. He threatened Saifuddin’s employer who tried to intervene. Saifuddin was taken to the pantry car where he was shot. Singh next moved to coach S6 of the train, where he shot a third passenger, Asghar Abbas Shaikh. Standing next to Shaikh’s body, he gave a communally charged speech, which was filmed by onlookers.
Borivali GRP has recorded statements from more than 100 witnesses and will be filing a chargesheet against Singh within 90 days.