GUWAHATI, August 23: Altogether four persons, including a CRPF deputy commandant, were killed and five persons were injured in five separate incidents in different places of the state during the past 24 hours. Deputy Commandant of 124 CRPF Rishpal Singh and constable Rajkumar Gar, the driver of the Gypsy the deputy commandant and his wife were travelling in, were killed on the spot, when a powerful explosion blew up the vehicle near the Maithang Bridge on the NH 52, about 12 km of Kakopathar police station in Tinsukia District this morning, police sources here said. Three others, including the wife of Rishpal Singh, Surjit Kaur, were injured. Singh and his wife were on their way to Tezu in Arunachal Pradesh from Mohanbari near Dibrugarh when the incident took place. The injured were rushed to the Dibrugarh Assam Medical College Hospital, where doctors say that they were out of danger. The truck, which was following the deputy commandant's vehicle escaped. According to a CRPF jawan who was in the truck, the blast occurred at a lonely place and there was no one in the vicinity at the time of the incident. Meanwhile, suspected militants of the National Democratic Front of Boroland (NDFB) shot dead a Hindi teacher in the heart of Nalbari town. An NDFB finance secretary was killed in an encounter with security forces at Balamguri under Bongaigaon police station yesterday, said police sources here. One carbine and ten rounds of empty ammunition were recovered from his possession.