A woman and her son who suffered burn injuries in the petrol bomb attack on a bus on Gaibandha-Palashbari road in Sadar upazila on Friday night died at Rangpur Medical College Hospital on Saturday, raising the death toll from the incident to six. The deceased were identified as Sonaban, 38, of Chandipur village in Sadar upazila, and her son Sujan Miah, 10. The former succumbed to her injuries at the burn unit of the hospital around 3:30pm and the latter around 7:30am, said sources at the hospital. Earlier, four people were killed and 30 others injured after miscreants hurled the petrol bomb at the Dhaka-bound bus of ‘Napu Paribahan’ carrying 50 day labourers under police escort in Tulshighat area of the upazila around 11pm on Friday. The arson attack left three passengers, including a child, dead on the spot, while another died on the way to the Rangpur Medical College Hospital. Twenty-two of the injured were taken to the medical college hospital where Sonaban and Sujan died on Saturday. The rest were admitted to Gaibandha Modern Hospital. The tragedy struck the victims while they were going to Dhaka in search of job, said police. Mosharraf Hossain, additional superintendent of police of Gaibandha, said police arrested seven people from different places for their alleged involvement in the arson attack. — Gaibandha, Feb 7 (UNB)