Aly Vander Hayden

Keyes kidnapped 18-year-old Samantha Koenig while she was working at a local coffee shop.

"You knew that was a grave. You just knew," said Detective Sergeant Mike Mongeluzzo.

"Open my trembling flower, or your petals I'll crush," he wrote.

Why do some killers like Ed Kemper go beyond murder and mutilate corpses? "The answer is, the killing alone is not psychosexually sufficient," said a forensic psychology professor.

"I came from my mother, and in a rage, I went right back in," said Kemper.

"I was getting less detectable," serial killer Ed Kemper said.

But Harold Cartwright said he "never felt unsafe" in Kemper's presence.

 Dubbed “friendly” and “cooperative” by law enforcement, Kemper divulged every detail of his crimes to law enforcement.

On the day of his murder, Brad McGarry had left to meet "DJ," a married man with whom McGarry had been having an affair for "years."

"It was all premeditated. I knew what I was doing," he said.