Going very off topic now lol.

Well, it may not have been 2.. may have been a bit younger (but i don't think it was) or even a bit older. But it did, and the owner alerted the offspring's owner (as most went to a single friend) and i believe one of the female offspring's went a similar way, or bred a daughter that was aggressive. I can't remember specifics any more, it was a good few months back when i was told of this, and i suffer from a relatively bad memory for details. Obviously the person stopped breeding from this rat immediately.
Strange, but not unheard of. At least this breeder had the sense to stop the problem

I wait to be proved wrong.....experience tells me otherwise I'm afraid.

I would guess it was at 6-9 months of age when it is expected that some bucks will have hormonal issues. The worst are castrated as they are unlikely to get along with others of their own species otherwise and not bred from. As I said before, late onset aggression as you described is almost certain to have a biological rather than psychological cause, perhaps a brain tumour as rats are so prone to cancers, which could easily be passed on familially as many of the cancers they are subject to are hereditable.

No, no it wasn't. I have had rats for a fair few years and i know the hormonal stages (got the scar from a buck to prove it!) and it wasn't. It was 2-3 years old, which was why i was so shocked and surprised to hear of it, and why it has stuck in my memory (cases of constant baby/teenagers getting hormonally aggressive really don't grab my attention any more, it's too common).
As far as i know the buck has no physical problems, and is alive today.