Most behavior depend on decision

In abhidhamma.-
There are 4 type of minds:

1. wholesome-root functional mind, good kamma.
2. unwholesome-root functional mind, bad kamma.
3. root's effect functional mind, kamma's fruit.
4. rootless functional mind, neither kamma nor fruit.

In one's life process:

1. human born just by wholesome kamma, but some organ, i.e. cyst, can arise by unwholesome kamma after born.
2. kamma has making body-sense for touching touch.

each mind's full process at body-sense:

3. contact of 3 dhātu: 1) touch arise & 2) body-sense arise & 3) 4th mind arise for to decide the kind of 3th mind, wholesome-effect/unwholesome-effect, that compatible with that touch (same time).
4. then 3rd mind knows that touch at body-sense, both are arose by kamma-cause.
5. then another 3rd minds know that touch by kamma-cause 2 times.
6. then touch is reached by 4th mind again for to decide the kind of 1st, 2nd, or 4th minds should arise to do new kamma in body.
7. then 7 times arising of 1st or 2nd mind and do new kamma.
8. then 2 times arising of 3rd minds.
9. then body vanished.
10. Above mind process, at body sense, can loop moreover trillion times per second, uncountable. There are more types of mind process than I show in this answer, this is just the example.

You can see that we receive fruit of old kamma and make new kamma in the same process and the same body.
His bad behavior is 1st, 2nd, and 4th mind. Just 3rd mind and a cyst organ are kamma's fruit.
So, the cyst organ is not a main cause of bad behavior. But previous bad behavior is the main cause of present bad behavior.
The cyst organ is just a fruit of the past bad behavior. It maybe one of side cause, but it is not the main cause. A human maybe feel very hurt and hard to decide to make arising of wholesome mind or unwholesome mind because of hurt at body-sense at 4th step but the decision is the 6th step. So, the 7th step is done by his decision in 6th step, not by kamma.
In the other hand: many example in tipitaka and commentary shown that there were many arahanta who were suffered at body-sense, but no one of arahanta have unwholesome-kamma, bad behavior.