The injured persons have been identified as Kenai Ram Mondal (38), his wife Sharmila Mondal (34), son Amit (12) and another relative Rang Lal (65), a senior administration official said.
While Kenai Ram himself sustained 15 per cent burn injuries, his wife and relative sustained 40 per cent burn injuries and the son, whose condition is stated to be critical, received 70 per cent burns.
Investigation into the matter is underway and his motive for taking the extreme step is yet to be ascertained, a police official said.