I haven't lost a kid but unfortunately know quite a few who have (none through murder thankfully!).
One, is one of my brother's best friend who passed away a couple of years ago from overdosis. Obviously since it was an overdose, technically he is his own ''killer'', the choice he made to consume drugs and drink at a party costing him his life at only 19, yet his parents were so devasted and angry that they took it out on their son's friends (not my brother as he wasn't at the party). My initial reaction when I found out that they had banned the two young men who had to go through the traumatic event of seeing their friend die and discovering his body the next morning from attending the funeral or even paying him their last goodbye, was lack of understanding, it seemed like they had taken their anger out on the wrong person (and I still feel like they have) but attending that funeral was the saddest thing I have ever had to attend, seeing this mum have to say goodbye to her son, knowing that day was the last day she would ever see him, it was heart-wretching and I understood that she needed to blame someone for something that seemed so senseless and unfair and who better than the guys she had trusted to hang out with her son and failed to bring him back alive? I could tell her heart, was filled with so much pain and anger (likely towards her son as much as his friends and the universe tbh) and I could understand why she felt the way she did.
I wonder where she is at now, and if she has somehow forgiven those guys and whether or not she regrets her initial reaction and not having them at the funeral (honestly I think her son would have wanted them there). Grief is SO personal and some need anger and to hate someone to try and need to make it a lifelong fight in memory of their loved on to get over it, and others have this need to forgive as a tribute to their kids personality and because they want positive to come out of that story.
I have had some traumatic events and stuff done to me and I found peace in forgiveness as hard as it was, would I forgive if someone killed a loved one of mine? It depends context is everything, an accident? Of course, cold-blooded murder with sexual assault? I doubt I ever could.
I would want my family to feel anger but eventually let go of it and find peace in forgiving, not sure I would want them and my murderer to become friends (especially if it was cold-blooded) though I wouldn't mind them befriending the parents as long as they didn't condone their child's action. Parents of murderer are definitely one of the many victims in that type of story and I can't even imagine how they must feel.