Sin is sin whether it is murder or telling a lie.
Genuine Repentance means to turn away from having the same desires that caused one to sin to begin with.
It is true that murderers in prison are stopped being able to be murderers physically, but they can remain murderers if their thoughts are still murderous. But if a murderer truly repents, they stop being and thinking of murderous things.
For the victims, where do many murderers find them at?
Many times they are found in places followers of God would not be at or associate with.
Dahmer met men at gay bars.
Christians do not spend time at gay bars.
Many prostitutes also are drug users.
Christians do not work as prostitutes or use drugs.
But I do believe children as victims have a special place in God's heart. Most children victimized are too young to make adult decisions and remain innocent.
And yes, there have obviously been Christian victims. And in many cases, after the fact, we read where they forgave the ones victimizing them before their death. We could even classify "some" of them as martyrs. Look at the Apostle Paul. He watched the stoning of Stephen and then met Jesus on the Damascus Road. But while Stephen was being stoned to death, he cried out to God to forgive everyone involved. That left an impact upon Paul and he became the greatest Author of the New Testament.