Four Central Industrial Security Force (CISF) personnel, including an Assistant Commandant, were killed in an alleged fratricide incident in Kathua district of Jammu division on Tuesday.The incident took place around 7 pm in the higher reaches of the district at the SEWA-2 hydro-project in the Basohli area.It has been learnt that the accused allegedly entered into a verbal confrontation with his colleagues before opening fire on them with his service rifle.The accused, a head constable, was arrested by the Kathua police and taken into custody.An Assistant Commandant, a Sub-Inspector and two constables were among those reportedly killed in the incident. Soon after the incident, the victims were taken to a health facility, where doctors declared them dead.There was no official confirmation on the identities of the victims.The accused is a 2009-batch head constable. The local police, besides the CISF, are carrying out separate investigations into the incident to ascertain the exact cause and sequence of events.However, officials said that after speaking to other personnel present at the site, it was believed that the accused started firing in a fit of rage after entering into a verbal argument with his colleagues.Many hydropower projects in J&K are guarded by the CISF to provide better security to these projects.