MUMBAI: A Mumbai magistrate on Monday extended, till August 11, the police custody of a Railway Protection Force constable Chetan Singh who had killed his supervisor and three passengers on a running train on July 31.

The Government Railway Police, which is investigating the case, produced him before the court after his initial remand ended Monday, and sought an additional seven days remand as it wanted to scan CCTV footage, identify more witnesses, etc.

However, the magistrate only allowed an extension till August 11.

The chilling incident took on board the Jaipur-Mumbai Superfast Express on July 31 morning, in Palghar as the train sped towards Mumbai and Singh was finally caught at Mira Road station in Thane.

After investigations and scanning certain videos on his alleged hate-comments against the minorities after the killings, the GRP added the Indian Penal Code Section 153 (A) for promoting enmity between different groups on religious grounds.

In the incident, Singh shot dead his immediate boss RPF ASI Tikaram Meena, and three passengers: Syed Saifullah of Hyderabad (Telangana), Asghar A. Shaikh, 48, of Madhubani (Bihar), and Abdulquader M. Bhanpurawala, 62 of Nalasopara (Palghar in Maharashtra).

Singh was nabbed after he jumped off the train near Mira Road station along with his weapon and later arrested late that evening, and a magistrate sent him to a week's police remand on August 1.