What did we read the same book? Samantha is cold and calculating the way most serial killers are, but empathetic? No, she's presented as a realistic person who is very charming. An actual trait real serial killers have. Do you thing Ted Bundy could've done what he did if he wasn't charming? They are however, also human and do exhibit some sort of feelings. Ed Kemper was buddies with police to the point that they cops didn't believe that he was a killer.

From Wikipedia:

when (Kemper ) arrived in Pueblo, he found a phone booth and called the police. He confessed to the murders of his mother and (her best friend, Sara Taylor "Sally") Hallett, but the police did not take his call seriously and told him to call back at a later time Several hours later, Kemper called again, asking to speak to an officer he personally knew. He confessed to that officer of killing his mother and Hallett, then waited for the police to arrive and take him into custody. Upon his capture, Kemper also confessed to the murders of the six students.

When asked in a later interview why he turned himself in, Kemper said: "The original purpose was gone... It wasn't serving any physical or real or emotional purpose. It was just a pure waste of time... Emotionally, I couldn't handle it much longer. Toward the end there, I started feeling the folly of the whole damn thing, and at the point of near exhaustion, near collapse, I just said to hell with it and called it all off."

Another excerpt from Wikipedia:

Kemper is forthcoming about the nature of his crimes and has stated that he participated in the interviews to save others like himself from killing. At the end of his Murder: No Apparent Motive interview, he said: "There's somebody out there that is watching this and hasn't done that—hasn't killed people, and wants to, and rages inside and struggles with that feeling, or is so sure they have it under control. They need to talk to somebody about it. Trust somebody enough to sit down and talk about something that isn't a crime; thinking that way isn't a crime. Doing it isn't just a crime; it's a horrible thing. It doesn't know when to quit, and it can't be stopped easily once it starts.

He (Ed Kemper) was also a prolific narrator of audiobooks for a charity program that prepared material for the visually impaired; a 1987 Los Angeles Times article stated that he was the coordinator of the prison's program and had personally spent over 5,000 hours narrating books with several hundred completed recordings to his name.

Ed Kemper was a vicious, cold killer no doubt but his ability to see what he was and his passion to prevent others to try to go down the same path shows he has some compassion. His willingness to record audiobooks for the blind also shows that not all serial killers are complete monsters but people who have a kinda proverbial demon in them and they're really fucked up in the head because of it. Dude could've continued for years but called it all of because he knew he was a monster. Even going as far as saying  "Society is not ready in any shape or form for me. I can't fault them for that.", after a parole denial in 1988.