Oh, come on. Your analogy is absolutely bogus.
The way an omnimax god can create a human is completely different from the way humans make another human being (I assume here you meant the old fashioned way). Additionally an omnimax deity knows the future in every little detail, whereas we do not.
So let's change the analogy a bit: this "father" doesn't make his kid the old fashioned way (with the help of a woman) but he assembles him atom by atom, molecule by molecule because he's a man with extraordinary capabilities.
Now, not only can this guy make a child from scratch, he also knows every little detail about the future of this kid, i.e. he knows the consequences of every change he makes to the design.
For instance he can see that changing certain parameters will make his son decline a friends offer to take cocaine whereas tweaking other parameters will change his future in such a way that he never meets this person.
So let's further assume that this father sees how the current makeup of his son will have the consequence of him shooting his family when he's 38 years 8 months and 11 days old but nevertheless decides to not make any further changes.
Now is the death of these people the father's fault (who could have made some more changes to his son's design) or is it the fault of the son?
I see you neither know, or understand God, or Free will. He said that He made man in His image and likeness. That means we have the same capacities as God. Perhaps you've missed the fact that Jesus is God. Gen 1:26 says, "Then God said, "Let us make man in our image, in our likeness, and let them rule over the fish of the sea and the birds of the air, over the livestock, over all the earth, and over all the creatures that move along the ground." It says Us. Jesus is that omnimax God you speak of. John 8:58 "I tell you the truth," Jesus answered, "before Abraham was born, I am!"
"this "father" doesn't make his kid the old fashioned way (with the help of a woman) but he assembles him atom by atom, molecule by molecule because he's a man with extraordinary capabilities."
Perhaps you missed what God said, "John 5:27 And he has given him authority to judge because he is the Son of Man." Mary was His mother.
Jesus was not born with the knowledge, understanding and wisdom of the Father. He was taught and developed the same Spirit as the Father. That was of His own Free will. It is written that He was tempted, yet did not sin. In John 9 God makes it clear that other men did the same. Free will means just that, a man is Free to choose between good and evil and that choice is based on the man's own choices of reasoning.
That "Us" that was mentioned in Gen 1 is the Trinity. Just as God is a trinity, so is man. You have a body that functions as a machine that supports the sentient, rational features of your mind. It provides for thinking, emotions, memories, Free will, ect... All those things that machine supports, that are the essence of your living being is your spirit. The soul is the machine that supports your spirit for eternity.
"Now is the death of these people the father's fault (who could have made some more changes to his son's design) or is it the fault of the son?"
Pehaps you think there's something wrong with BTK's machinery, that he just wasn't loved enough, he was deprived, or some other rubbish. There are those that are deficient, but that doesn't apply here. Nor does it apply to such people as the 'toon and his wench. The fact is that he made his own choices and the prominent choice that sticks out is that he places no value on the life, or rights of others. That's not God's doing, his parents, or anyone elses. It's his own doing, because he made his value choices by his own free will.
The answer is obvious. If the father controlled the kids destiny by construction, the father is at fault. Next.