"He became enraged after she would not do with him what she did with the other two."
Please explain what you mean by this.
I know you are not asking me, but I took that to mean sex of some form.
I do sometimes wonder if there was a racial component to this. The other men are both AA and DS might have felt particularly slighted/engraged if he has a racist mindset.
It appears SS did prefer AA men (father of some if not all of her children) so that scenario makes a lot of sense. DS even looks a bit disgruntled in the surveillance video.