A Railway Protection Force jawan (RPF), who on Monday shot dead four persons across nine carriages on a running express train from Jaipur to Mumbai, was remanded to police custody till August 7.
Among those killed were an assistant sub-inspector (ASI) Tikaram Meena and three passengers, all Muslim men.
Two of the deceased passengers have been identified as Abdul Kadarbhai Mohammed Hussain Bhanpurwala (48), a resident of Nalasopara in Palghar, Asgar Abbas Sheikh (48), a resident of Madhubani in Bihar, and Sadar Mohammed Hussain.
RPF Constable Chetan Kumar Choudhary first shot dead ASI Tikaram Meena in coach B-5. He then shot and killed Abdul Kaderbhai Bhanpurwala, who was travelling in the same coach.
Choudhary then walked across four coaches until he came across a passenger in the pantry car, identified as Sadar Mohammed Hussain, and shot him dead.
Choudhary next walked across two other coaches before shooting dead his third victim, Asghar Abbas Shaikh, in coach S-6, according to media reports.
Reports said that the deceased passengers sported beards and looked identifiably Muslim.
The Railway Board has set up a five-member committee to conduct a 'comprehensive inquiry' into the incident.
The members of the high-level committee reached Mumbai on Tuesday to begin the investigation.
The Government Railway Police will also scan the footage of CCTV cameras on the train, a senior GRP official said.
The probe committee comprises the principal chief security commissioners of the Western Railway and the Central Railway, the principal chief commercial manager of the North Western Railway, the principal chief medical director of the North Central Railway, and the principal chief personnel officer of the West Central Railway.
According to railway officials, the panel has been asked to submit its report on the incident to the Railway Board in the next three months.
In a video shared on social media, Choudhary can be heard hailing Prime Minister Narendra Modi and Uttar Pradesh Chief Minister Adityanath as the body of one of the Muslim men lies at his feet.
"They operate from Pakistan, this is what the media of the country is showing," Choudhary is heard saying in the video. "They have found out, they know everything, their leaders are there. If you want to vote, if you want to live in India, then I say, Modi and Yogi, these are the two, and your Thackeray."
The accused constable was nabbed by the police with his weapon while trying to flee after passengers pulled the chain of the train which stopped near Mira Road station (on the Mumbai suburban network).
Meanwhile, a magistrate court on Tuesday remanded the accused constable to police custody till August 7.
The incident drew sharp reactions from Opposition leaders who blamed the ruling Bharatiya Janata Party (BJP) and polarised news media for the hate crime
"The cold-blooded murders carried out by an RPF constable is the result of a hyper-charged and highly polarised news media and social media atmosphere," Congress MP Jairam Ramesh wrote in a tweet. "The genie of hate is now out of the bottle and it will take a lot of collective effort to put it back in."
Congress President Mallikarjun Kharge said, "What is going on in some parts of Haryana or what the RPF constable did is like giving deep wounds on the chest of Mother India."
All India Majlis-e-Ittehadul Muslimeen MP Asaduddin Owaisi described the incident as a "terror attack targeted at Muslims".
"It is the product of continuous anti-Muslim hate speech & unwillingness of Narendra Modi to put an end to it," the All India Majlis-e-Ittehadul Muslimeen party leader said. "Will the accused RPF Jawan become a future BJP candidate? Will his bail be supported by the govt?" he tweeted.