Officials said the incident occurred early in the morning when constable Sonu K Rathore fired two rounds on himself from his INSAS rifle at a forces' camp duty area in the district.
They said Rathore's unit, Sashastra Seema Bal's 38th battalion, was on election duty in Cooch Behar.
Local police officials and senior SSB officers reached the spot. A Court of Inquiry has been ordered to go into the reasons as to why Rathore took the extreme step, officials said.