According to the police, the murder is allegedly the handiwork of another prisoner, Arun Chaudhary, who was recently transferred the facility from Jammu and Kashmir.

The incident occurred around 2.00 am in Chakki No 2 of security ward 3B, located near Barrack No 3. During a heated altercation, Chaudhary allegedly stabbed Rehman with a sharp-edged weapon, killing him on the spot.

A third inmate, Soeb Riaz, was present at the time of the incident, but was intimidated and threatened with death by the accused, a senior police officer said.

Yashpal Yadav, spokesperson with the Faridabad police said a case of murder has been registered against Arun Chaudhary at the Sadar Ballabgarh police station following a letter from the Faridabad District Jail administration.

"Chaudhary already faces murder and attempt to murder charges in eight cases across Jammu and Amritsar. He was shifted from Kathua to Neemka in October 2024. The matter is under investigation," the spokesperson added.

Rehman, a resident of Milkipur in Uttar Pradesh's Faizabad, had been in custody since June 2025. He was apprehended in March that year from Pali village near Faridabad during a joint team by the Gujarat Anti-Terrorism Squad and the Haryana Special Task Force (STF). At the time of his arrest, police recovered two hand grenades and two mobile phones. An FIR against Rehman was filed at Dabua Police Station in Faridabad.

Haryana STF had received information that a sleeper cell could be supporting Rehman as they provided hand grenades to him, sources had said. The hand grenades were later defused by bomb disposal squads.

In the mobiles, some incriminating videos were also found, sources had said, adding that they also found he had shared several videos with a terror outfit.

Officials had stated Rehman was involved in a conspiracy to carry out an explosion in Ayodhya. He was suspected of having links with Pakistani intelligence agency ISI, an STF official had said on the condition of anonymity.

His parents had however had rejected the allegations, stating he was not involved in any terror activities.

The accused, Arun Chaudhary alias Abbu Jat, hails from RS Pura in Jammu. He gained notoriety following the murder of Akshay Sharma, a resident of Samba. Arrested after an encounter in Punjab in 2023, Chaudhary was initially lodged in Kathua jail.

His transfer to Haryana in October 2024 came after a controversial incident where he went live on social media from inside Kathua jail, alleging that jail staff accepted bribes to provide mobile phones and other facilities.

The murder inside a high-security ward has raised serious questions regarding prison surveillance and safety of inmates.

"An internal investigating is underway to determine if the murder was linked to Rahman's legal cases or was the result of a personal rivalry," said a jail official.

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)