He was not a common criminal. I think he came from a middle class normative family background. He was fairly intelligent and educated from what I've read. He did do the crimes, I think he killed at least three people for not very good reasons. He sought connection to gangsters for whatever reasons, probably to feel empowered by these connections. The murders he was involved in don't seem gang related. Gangsters normally don't deliberately kill civilians even if they spilled beer on their jacket, they might beat them up and extort them but killing is just too risky.