Investigators also revealed that seven years later, Bishop was the prime suspect in a 1993 mail bombing attempt on a Harvard Medical School professor.
"I just feel angry," LaTasha Davis, stepdaughter of shooting victim Maria Davis -- one of the dead -- told "Good Morning America" today. "How did she even get a job working at the school when she had that type of background?"
She was reportedly upset about being denied tenure at the school. Husband Anderson told the Chronicle of Higher Education that one of her bosses had sent her negative e-mail they called "nastygrams."
When she called him less than an hour after he dropped her off for the faculty meeting Friday, Anderson said, Bishop made no mention of the shootings and told him they were still on for their date night.
LaTasha Davis and her sister, Melissa Davis, told "Good Morning America" they believe Bishop was able to get a list of which professors did not vote in her favor for tenure and used it to plan the shooting.
Also killed, according to the Associated Press were, Gopi K. Podila, the chairman of the Department of Biological Sciences, and faculty member Adriel Johnson.
Melissa Davis said she had taken a class with Bishop and found her to be disorganized and prone to rambling.
"I remember thinking, 'I'm glad I'm not sitting in calculus or anything like that,'" she said.
Melissa Davis said she hopes the shooting will lead to more thorough background checks for its faculty and staff.
"We both loved Maria and believe she never should have been killed like this," she said.
The Davis sisters remembered their stepmother as a calming presence in the house. Maria Davis married their father after the girls' mother died when they were teenagers.
"Maria came in with this gentle kind heart," Melissa said, adding that she never left the house without telling her family that she loved them.
In contrast, Amy Bishop seemed to harbor anger and resentment. Though investigators say they will not re-open the investigation into the 1993 attempted mail bombing of a Harvard Medical School professor, those who worked with her at the time say it was terrifying.
"We were completely rattled -- it was the time of the Unabomber," former co-worker Sylvia Fluckiger said of the two homemade pipe bombs that were sent to the professor's house. The bombs were later detonated by the bomb squad.
Once again, Bishop was never charged due to lack of evidence. And, authorities, say the motive seemed to be eerily similar to the potential motive in the Alabama rampage -- Bishop was reportedly upset about a negative evaluation she was expecting to get from the targeted professor.
Fluckiger, who worked with Bishop at a research lab, said she remembered Bishop and the professor having a disagreement.
"I just know there was an argument ... that the police questioned her," Fluckiger said. "She had told me they talked to her about those bombs. She had like a grin on her face."
Investigators said that during the investigation into the bombing, they found a novel on her computer that described a scientist who had shot her brother and then sought redemption.