The son of a victim of a suspected hate attack on a Mumbai-bound train last month has said the family was "not feeling safe here" and is "planning to shift to another country".

Railway Protection Force (RPF) constable Chetan Singh has been arrested on the charge of gunning down a senior colleague and three Muslim passengers in different compartments of the Jaipur-Mumbai Central Superfast Express on July 31.

The victim's 34-year-old son, who has not been identified, said: "We are feeling unsafe, why would we stay here? Planning to shift to another country. Obviously, our house will be here (in India) and will come for a few days."

The murdered passengers were identified as Abdul Kadarbhai Mohammed Hussain Bhanpurwala, a resident of Nalasopara in Palghar district; Asgar Abbas Sheikh, who hailed from Madhubani in Bihar; and Sayyad Saifuddin, originally from Bidar in Karnataka who had settled in Hyderabad. RPF assistant sub-inspector Tikaram Meena was the first to be killed.

A video clip featuring the purported graphic scenes inside the train compartment on July 31 had shown a person in uniform saying in Hindi: “If you want to vote, if you want to live in Hindustan, then I am saying, Modi and Yogi, they are the two, and your Thackeray.”

On Friday, a court in Mumbai did not allow the victim's son to attend remand proceedings when Singh was produced before it at the end of his police custody. The RPF cop was later sent to jail under judicial remand.

Citing security reasons, the magistrate had earlier disallowed media persons and lawyers not connected with the case from entering the courtroom.

The court also refused to give permission to the Government Railway Police (GRP), which is probing the case, to conduct brain mapping, polygraph and narco-analysis tests on the accused.

Anxiously waiting outside the courtroom, the victim’s son, who works in Dubai and recently returned to India, said he had visited the police station in suburban Mumbai that is handling the case multiple times and met the investigating officer, but did not receive any cooperation.

The GRP has booked Singh under Indian Penal Code Section 153A which relates to promoting enmity between different groups on grounds of religion, besides provisions related to murder and kidnapping.

Singh was arrested 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.