Mary Ellen O’Toole was enjoying wine and cheese with her neighbors one evening when the phone rang. It was a serial killer.

“We were just having a nice night, and I answered the phone, which I don’t normally do, and they go, ‘Oh, who was that?’” O’Toole recalled with a laugh. “It did scare the heck out of my neighbors: They got up and left!”

O’Toole said her conversation with the jailed killer, whom she declined to identify, was “easygoing.” They exchanged pleasantries, she said, and then he aired his literary aspirations.

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“He wanted to resurface again. He had gotten a lot of press before, and his notoriety had sort of calmed down, and it was right at the time that my book had come out and so I think he saw the potential there of my helping him to write a book,” said O’Toole, a retired Federal Bureau of Investigation profiler and author of Dangerous Instincts: How Gut Feelings Betray Us.

“What is it, the Berkowitz Law? Son of Sam law? Killers can’t profit on their crimes, but it doesn’t mean they can’t try. But I think that was the goal,” she said, adding: “That was not going to happen.”

O’Toole, one of the first women in the FBI’s Behavioral Analysis Unit, spoke with Newsweek at her home in Virginia, where she served coffee and ham-and-cheese quiche, as well as chocolate chip cookies. Much of her work over the years has involved finding and/or interviewing serial murderers, such as the Unabomber, Zodiac, Green River Killer Gary Ridgway and the Monster of Florence.

O’Toole’s phone has been ringing quite a bit of late, but most of those calls have nothing to do with serial killers: In addition to psychopathy and crime scene behavior, O’Toole is one of the world’s experts on mass and school shootings. In the wake of the Columbine massacre in 1999, she was the lead author of The School Shooter: A Threat Assessment Perspective. While the document was based on K-12 incidents, it has become the preeminent guide for figuring out whether this kind of troubling behavior might turn murderous.

So, whenever there’s a mass or school shooting—or a peculiarly bizarre killing, such as Vester Lee Flanagan’s live-TV attack in Virginia on August 26 that left WDBJ7 reporter Alison Parker and crew member Adam Ward dead—O’Toole is the go-to for media outlets.

But it’s not like her demeanor resembles that of the many criminal profilers seen these days in popular culture. She didn’t comport herself with any sort of grizzled nonchalance or paranoia when it came to the killers she’s dealt with. She also did not seem to have inappropriately intimate relationships with her subjects or colleagues, in the way so many woman cops are annoyingly portrayed in film. Of course, she was serious—we were talking about serial killers and school shooters, among other grave topics—but she exuded an enthusiastic warmth and a disarming quirkiness.

Her aesthetic also testifies to this: While she donned a navy-gray FBI pullover, she also sported a burgundy bobbed haircut and black nail polish. And even as we spent hours discussing everything from serial murder to psychopathy in ISIS to campus sexual assault, we also spent a considerable amount of time chatting about her cats Googles, Sissy and 3-month-old Elvis, as well as the ferals outside Garfield, Merlegirl, and Bootsy. (Her coffee mugs were also feline-themed.)

While appearing as an expert on CNN, CBS, Fox and other networks recently, O’Toole explained how Flanagan’s troubling behavioral history culminated in his killing Parker and Ward.

“He had a pattern of this behavior where he collected perceived injustices and insults from people,” she told Newsweek.  “You could sort of see over the years how he evolved into becoming worse and worse, angrier and angrier. He couldn’t hold a job. He was the victim. And it was everybody’s else’s fault.”

Many such “injustice collector” mass shooters claim they acted violently because they had always been put down, she said. Like Flanagan, the shooters often write manifestos explaining why they, and not the people they killed, were the victims. South Carolina church shooter Dylann Roof, for example, had posted a racist screed online, and Santa Barbara shooter Elliot Rodger penned a manifesto detailing his hatred of women.

Part of O’Toole’s job is to let people know they can take steps that could potentially prevent injustice collectors from becoming violent.

The Roanoke TV station that had fired Flanagan could have assessed whether he posed a danger post-firing. His employers knew about his track record of volatile behavior, including in the workplace, and should have checked in on him post-termination to see if he had worsened, she said. Those check-ins could have been as simple as phone calls.

Instead, seemingly nobody knew what Flanagan was doing: that he had stewed in anger for two years after being fired and had bought a gun.

O’Toole continues to consult on cases. Last winter, she became the program director in George Mason University’s Forensic Science Department. She’s also editor-in-chief of Violence and Gender, a quarterly journal that launched in 2014. One of the most viral Violence and Gender articles discussed a small study revealing that approximately a third of college men said they would rape a woman if they could get away with it.

Given all of her present work—profiling, editing, teaching at the FBI academy and directing an academic department—I got the impression that O’Toole is busier in retirement than most working people. She’s more than OK with that. When she was working full-time for the FBI, she couldn’t pursue a lot of side projects. She can finally do as much as she would like.

“Now it’s like I’m a kid in a candy shop,” she happily admits.

The weirdest thing about her “retirement”?

“Well, I cannot tell you how many people come to the door during the day now that I’m retired,” she said. “A lot of people come to the door. And some of them are just plain strange.”