"Huntsville is not a very friendly community in certain specific areas," he said. "I have a gut feeling that she may have had a weapon for stalkers."
"I don't know if she would have shared that with [her husband] or not," said Anderson Sr. "It was an off the cuff remark to me about someone in her campus neighborhood she had to keep an out eye out for."
Anderson Sr., 71, said that his immediate worry was for the "safety of the family," not knowing who might be "revengeful."
When asked if she had personal issues, he said, "I think that's probably true," especially after she faced a prospect of unemployment after being rejected for tenure.
Whether that event alone could have triggered an act of violence is unlikely, say mental health experts.
But many psychiatric disorders can go undiagnosed for years, especially for those who lead insular lives.
"People in science and computers are solitary people," said Dr. Igor Galynker, associate chairman for the department of psychiatry and behavioral science at psychiatry at Beth Israel Medical Center in New York City and professor of psychiatry at Albert Einstein college of Medicine. .
"They work in solitude and they don't need to interact in complex social situations and can be paranoid for a long time without someone realizing."
Schizophrenia can be marked by social isolation, odd behavior, "strange disordered" thinking and speaking, poor hygiene and lack of friends, according to Galynker.
Often people don't notice signs until more serious symptoms emerge.
"Brilliant scientists are supposed to be crazy," he told ABCNews.com.
John Nash, the Nobel-winning economist from Princeton, portrayed in "A Beautiful Mind," could be coherent in his field, even as he suffered from schizophrenia.
Anti-social personality disorders can also result behavior that is "incompatible with laws," like stealing or shooting, he said. And in narcissism, a person can display disregard for the feelings of others or seek self-aggrandizement and, like Bernie Madoff, can be "very charming."
Psychotics like Seung-Hui Cho, the student who who killed 31 at Virginia Tech in 2007, are particularly dangerous.
Killers like Cho view others as inconsequential and often humiliation can set off a psychotic depression that could make a person violent or suicidal, said Galynker.
"Look at a 3-year-old before their conscience is developed," he told ABCNews.com. "You want to escape bad consequences, and you don't have the internal mechanism to want to be good. If you do become angered or enraged, nothing inside of you is telling you that it's bad."
"There is the fear of getting caught, and then you get away with it and you harbor a sense that all these other people are crazy," said Ochberg. "There's a sense of entitlement."
Any of those psychiatric disorders could justify an insanity defense -- lacking the capacity to know right from wrong , according to both psychiatrists.