As a Christian I believe we are to forgive folks who honestly and sincerely request it. True repentance must exist, and no penalty should be lessened in the process. NONE! (on this earth)
Now, as an individual at a time late enough after the death of the daughter, the parent may be moved to be forgiving personally.
Not waiting very long, and publicly professing forgiveness, amounts to nothing less than complete buffoonery and the ultimate betrayal of the daughter.
He may be trying to be a good Christian, but his daughter deserves better than this.
The killer is dead, his daughter is dead. The killer is beyond forgiveness, her father is avoiding unrequited hate and it is the Christian thing to do. His daughter no longer cares and from what I understand, is in the arms of her Savior.
Also, I don’t recall anywhere in the scriptures where Christ said that the State should not seek justice.