The incident took place near 1st MLP Battalion, Mawiong last night when the two were returning from Guwahati after a protocol escort duty of a senior government official.
Havildar S Snaitang fired with his service revolver at constable Randhir Kr Singh the vehicle injuring him seriously, SP (City) Vivek Syiem told PTI.
Singh, who suffered two hits on the head, was hospitalised.
It is yet to be clear what led to the firing, Syiem said.
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