Have you read the book “Who killed Karkare?” by S. M. Mushrif? I have only read about it, but taking in consideration that the number of members of RSS is about 5 million, it only requires a few parts of a percentage of them to make a sufficiently large hyper nationalistic group. It is statistically not unlikely that such a group would be engaged in political violence.
This https://en.wikipedia.org/wiki/Abhinav_Bharat is an example of such a group. Members can drift between such groups and we should assume that IB is trying to infiltrate them.