Is there such a thing as a parole w/o a Parole Board?

I have a childhood friend that killed somebody about 20 years ago. He was caught immediately, and went to prison. After 5 years, mol, he had a chance for parole, the family of victim was there, and he was denied parole. Same song, second verse next time. Next thing I heard, about 10 years after he went to prison, he was getting released. I also have it in my head that there was no parole hearing. Is this possible? I do know that the governor hadn’t given him a pardon, and that he was on probation for some few years.
Does the warden/prison/corrections department have any discretion in these things?

I don’t know what state you are in but in California, prisoners are given one day Good Time Credit for each day they are in Prison (jail has a different scheme) that means most prisoners are released upon completion of half their sentence. They are placed on parole but the parole board does not get involved. If they have strikes under the three strikes law they must complete 80% to 85% of their sentence. Unless they were sentenced to an indeterminate sentence like 25 years to life the board does not get involved. That means they must complete 25 years before they are eligible for parole.

Nobody but the sentencing judge has discretion in these matters in California. There are strict sentencing schemes that determine a prisoners release date. The prison may deny goodtime credit for infractions of prison rules but they can’t let you out earlier than statutes permit.