The bomber is the one who prepared the bomb for Meera. So at that time he was still working with Munim and Mehak. Then he was captured and tortured. Munim and Mehak thought that he was already dead. This indicates that these two were still in contact after Dev met Munim. Given that at that time Mehak was still considered as a criminal and was linked to Chakravuyh, the police must be keeping an eye on her. How come she could still be involved in Chakravuyh?
I think he is not responsible for Meera's death. Maybe he had already prepared bombs some weeks before he was captured. So, it is only Munim and maybe Mehak who are responsible for Meera's death. It is only recently that he escaped.