At least from what I've seen these sorts of things are systemic issues, and it is extremely rare for such problems to be caused by a single bad apple.
Again, not trying to discount your personal experiences or lessons, but I'd just be very wary of assigning scapegoat status to a single person for what is clearly a toxic workplace in general ("Management stayed quiet and attempted to push it under the rug for a bit", "Workplace politics were on the rise", etc etc). Often times this mentality plays to the people in power who are responsible for the lack of safeguards, and when you don't fix the underlying causes you're essentially just relying on HR to filter the "bad apples" out of the hiring practice... and we all know how much of a crapshoot hiring in tech is already.
Last, I'd re-examine your impulse to go out and celebrate when this guy was fired. I obviously don't know the details here, but it definitely sounds like an "us vs him" mentality was being fostered, and that could have very well contributed to the exacerbation of this guy's toxic behavior. Often times these sorts of people are just desperate for attention or social contact, and the only way they've figured to get a consistent response from people is to piss them off. Disengaging and relying on "management" to solve these issues very often can make a problem worse. Other times these people can be simply responding to being bullied themselves, often simultaneously, by other groups within the company, or are reacting to problems in their personal lives. These explanations are not absolving them of responsibility for their actions, but it's important to realize that most assholes aren't genuinely bad people, they're just normal humans like you and I who respond to stress and stimuli in a poor way.
Going to the guy as a group and discussing his behavior, while uncomfortable, often can be very illuminating and solve issues that would have just festered until someone was forced to be fired or leave. Worst comes to worst you'll immediately realize the situation is untenable at that point, and the solution will be quite obvious.
Again, disclaimer, I don't know the specifics here and I don't want to indict the parent, but let's make sure we don't use the above example as a primer on how to deal with toxic colleagues in general.