"We were talking and the next thing I knew," Grossman remembered, "he just kind of raged and he got a gun and put it to my temple.'"
Walker's ex-wife now believes one of his alternate personalities was in control at that moment. "There was somebody there that was evil."
Walker says he does not remember the event, and many others, including — shockingly — the highlight of his collegiate football career, winning the Heisman Trophy in 1982.
Periods of memory loss are one of the symptoms of the disorder. "A lot of the things that happened there that she may remember, he doesn't remember because those were the things that were being done by the alters that were so unlike him," Mungadze explained.
"Do you not remember something like that because you think that was another alter," Woodruff asked, "or do you want to get out of having to talk about it?"
"No, no, no, no," Walker insisted. "I'm talking about everything else. If I can remember it, I'll talk about it."
There were other incidents Walker does not recall. "I was pregnant and it was probably 100 degrees out," Grossman said. "Herschel was dressed in a full sweat suit, tights, sweats, jacket, and he was running through the house. ... he said, 'Close the door. I am having bad thoughts. I am thinking I am going to hurt you.'"
On another occasion, Walker threatened to kill his wife, his wife's friend and his therapist in a therapy session.
Mungadze said he saw many alters on that day: a raging one, a protector, and finally a child when Walker hit a wall and broke his hand.
Walker does not deny the events, but says he has no memory of them. "No, I don't remember that, but I probably did it."
After a hospital trip to treat Walker's hand, Grossman remembers Walker calling her, "'Miss lady."
"And I said, 'My name is Cindy.' And he said, 'Herschel's hungry. Do you know what he likes to eat?'" she recalled. "I said, 'Well, I know he likes wings."
"People outside — Cindy, Doctor Jerry — may have seen that, whereas I may not remember a lot of that," Walker told Woodruff. "And I hear them say that, and I say, 'Oh, that's weird.'"
It is difficult to understand how someone with this disorder sees the world.
"It's just personalities that can do different things for you," Walker said.
Mandgadze offers a metaphor. "It's like a teacher in a classroom, a very chaotic classroom, where the students do what they want to do — hit each other, scream ... we would like them to have some way of managing his alters, almost like a teacher manages students."
"But we all do that. We get angry or we get frustrated; our eyes change, our face changes, right?" Woodruff asked Mungadze.
"No, not to that extent," Mungadze replied.
"There are a lot of doctors that say, 'We don't think this exists, this D.I.D.," Woodruff asked Grossman.
"That makes me kind of angry," replied Grossman. "I just know he has it. I know what I saw."
The Diagnostic and Statistical Manual of Mental Disorders defines the disorder as "the presence of two or more distinct identities or personality states that recurrently take control of behavior." The alternate identities "frequently have different names and characteristics that contrast with the primary identity."
In the book, Walker names around a dozen alters, including "The Warrior" who handled football and the pain that came with it. "The Hero" took over in public appearances.