RAW has a history of sponsoring extremist terrorist organizations in neighbor countries. There is allegation that ABT, HUJI, JMB in Bangladesh were created and funded by RAW. Instead of running false flag operations with its own team, it is much easier to run genuine terror operations by gullible true believer extremists, if they can be controlled through proper handlers. There is allegation in Bangladesh that ABT was behind killing of at least 5-6 atheist bloggers, which became great international news in Western/US/global media, one of whom was a visiting US citizen of Bangladeshi origin. What would be Indian interest to conduct these killings? Now what country always wants to show that Pakistan and Bangladesh are terrorist infested unsafe failed states? That would be India of course. So India is the prime beneficiary from these killings and their wide exposure in global media. So when one needs to solve a crime, the first place one has to look is to who gets benefited from the crime. India certainly fits that description more than any other country.
So just like I would not be surprised if it was uncovered that India was behind the ABT group, responsible for killing Avijit Roy:
Avijit Roy - Wikipedia, the free encyclopedia
I would not be surprised if RAW was the mastermind behind the killing of Sabeen Mahmood. RAW planners are expert at creating international news to manipulate public perception and targeted killing is one of their most effective tools, which we can already see in Bangladesh.