A Border Security Force (BSF) trooper killed three of his colleagues with his service rifle before committing suicide at a border outpost in Tripura, a police official said on Sunday. "Sishu Pal, after a brief quarrel, opened fire on his colleagues including a head constable before killing himself at the Maguruli border outpost" in Unakoti district, the official said. The incident occurred on Saturday night. The victims belonged to BSF's 55 Battalion. BSF Deputy Inspector General Mrityunjaya Kumar told IANS: "Investigation of the incident is on. A detailed report is awaited."