What does this sentence mean?
So I have been reading a book and there 's I don't quite understand.
The text goes:
"The big kid is Roland. He had dreams of being a military boeuf but apparently had too much testosterone, or steroids, or a combination of both, leaving him a little too scary even for the military. Like Connor, Roland got into fights at school-although Connor suspected Roland's fights were much, much worse. That's not what did him in, though. Roland had beaten up his stepfather for beating his mom. The mother took her husband's side, and the stepfather got off without warning"
I want to know what "That's not what did him in" means. At first I thought it meant that he was sent to prison, but then I realised that the sentence had to be "That's not what GOT him in". I looked up everywhere on the web and I couldn't find any satisfying results. Thanks for responding!