The unusual incident happened along the border between Assam and Mizoram states in north-eastern India. Officials from both sides, including chief ministers, have accused each other of provoking violence. The firing incident follows months of simmering tensions over a long-running border dispute between the two states. The two sides have often sparred over it, sometimes violently. But this was the first time police in the states had fired at each other in a direct confrontation. The officers killed in the attack were from Assam.