He is not going to be in his 40s, late 30 maybe, but he would have migrated to more serious crime (like killing a person), if he was in his 40s, because drive by knifing (I think that's the term) seems to callous and immature to a 40 years old. I mean this is along the same line of crime akin to driving by you and throw stone or egg at you (Albeit a bit more serious because he is stabbing the women) That is why I pegged his age between 20s-30s.
He can be of drug and alcohol abuser. But he was most likely not doing that unless these crime is completely random, and not knowing much, I cannot say it is.
I don't think he was dumped by his partner, in fact, he seems like the kind will choose spouse that do take some abuse sometime and of low self esteem, he exert dominant trait (He choose the time, place, and which woman to attack), which mean he like to get things in control. Which mean he would probably not choose women that goes with him he cannot control (ie the kind of woman who will dump him) These behaviour usually come from sexual abuse in younger ages, possibly by a female family member (ie his mother or grandmother or sister abuse him when he was a kid)
To me, this is either a thrill attack (which would mean he is in his early 20s.) or targeted attack (which would mean the stuff that I said before) but he would most likely continue with his attack until he is caught. Highly likely if he is targeting these women, he would change his appearance (the bike he drove or the helmet he wore) but uses the same MO. What important for him is the process of attack, not before and not after. So unless he find another way to feed his need or was physically stopped, he will continue his attack
This is a different perspective in serial killers, for a serial killers, these people think the why is very important, why they kill people, they wanted other people to know why they kill people (This is called Serial Killer Initiative/Incentive) For a normal person, people will be appalled by these act but most don't care about why they start killing people. And in the case of Ted Bundy, this is the inner entity and in the case of the Zodiac, it was the need, he think he is born to kill, on one hand, he will challenge anyone to catch him, on the other hand, he would think he is in control of the situation and leak information to you, not much, but just enough to spike you.
To a normal people like us, these is just some sick note, because we probably won't care why the Zodiac kills, to the Zodiac killer, his communication is a manifesto, which he want the world to know why he is doing what he is doing.
Depending on his MO and if I have more information on the case, he may not just wanted to wound people, doing this is what we call stepping case, you get the thrill and you weren't caught, if he thinks this is not a challenge anymore, he will progress to other crime, like raping a woman or killing one eventually, again, I do not have the case file and I based my point on 2 news article I read (I cannot even spot where he strike and the timeline) so I may be wrong on this.
