Sudip Datta Bhowmik, 50, was a crime reporter for the popular Bengali daily Syandan Patrika. The accused soldier, Nandu Reang, who was with Tripura State Rifles, a paramilitary force engaged in counter-insurgency operations, has been arrested.
The shooting took place this afternoon inside the headquarters of 2nd battalion of TSR at RK Nagar, around 30 km from state capital Agartala.
Mr Bhowmick's employers said he was following a lead and had gone there to get more information.
Eyewitnesses reported that the journalist had an argument with the Nandu Reang. As the exchange grew heated, the soldier pulled out his service revolver and shot Mr Bhowmick.
The journalist died at the spot. The police who were looking for his cellphone for clues, say it is missing.
Nandu Reang was overpowered immediately and taken into custody, said Abhijit Saptarshi, a senior police officer. "The motive of the killing or what really happened is not clear. We have started investigations and have taken the jawan in custody," he added.
In September, a 28-year-old television journalist, Santanu Bhowmik, was killed while covering a clash in Mandai, 35 km from Agartala. Two men - who allegedly belong to the Indigenous People's Front of Tripura (IPFT), a tribal political party demanding a separate homeland - were arrested.