Four CRPF men were killed and one severely injured in their sleep when a jawan opened fire around 12.15am on Tuesday at a camp in Dantewada district of Chhattisgarh.
Although unconfirmed reports said Tiwari had had altercations with the victims, CRPF officials ruled out hostility as a reason behind the killings.
SP Narendra Khare said, "Constable Deep Kumar Tiwari, who was sick for a couple of days and not on duty, was soon overpowered. He had claimed to have been under mental stress."
"We have instituted a court of inquiry. There was neither an issue of pending leave nor was he harassed in any way. Only after investigations, we will know the actual cause of the incident," said IG, CRPF, Zulfiquar Hasan.
"Tiwari, who is from Uttar Pradesh, has been arrested. Further investigation is on to ascertain the cause," the SP said.
The shocking incident of four paramilitary personnel killed in fratricide inside the heavily guarded camp of CRPF has been cited as the first of its kind in the red zone of Bastar.
In September, the home ministry called a meeting to discuss fratricidal killings and suicides in forces.
The ministry figures showed 400 paramilitary troopers died in fratricide incidents or committed suicide since 2009.