The 32-year old Manimaran was on security duty for a serial bomb blast convict Abu Dahir, who is being treated at a city private hospital.
As routine, Manimaran had gone to deposit the 9 MM pistol after turn of his duty on Tuesday last and before doing so, he checked whether all bullets were removed from it by pulling the trigger.
When he pulled the trigger there occured a gun shot, which pierced a wall. However, nobody was present there at that time, they said.