Grieving relatives of three professors gunned down at a university faculty meeting questioned why their accused colleague was hired despite a dispute with a former boss who received a pipe bomb and the shooting death of her brother.

Amy Bishop is charged in the three deaths and the wounding of three other professors at a meeting Friday at the University of Alabama in Huntsville. She was vocal in her resentment over being denied tenure and the looming loss of her teaching post, though relatives and students said she had never suggested she might become violent.

The outbreak of violence was followed by weekend of revelations that Bishop, who is in her 40s and has four children, had a difficult past that she did not discuss with her Alabama colleagues.

In 1986, Bishop shot and killed her 18-year-old brother with a shotgun at their Braintree, Massachusetts, home. She told police at the time that she had been trying to learn how to use the gun, which her father had bought for protection, when it accidentally discharged.

Authorities released her and said the episode was a tragic accident. She was never charged, through current Braintree police Chief Paul Frazier questions how the investigation was handled.

In a second incident, The Boston Globe reported that Bishop and her husband were questioned by investigators looking into a pipe bomb sent to one of Bishop's colleagues at Children's Hospital Boston in 1993. The bomb did not go off, and nobody was ever charged.

Bishop's husband, James Anderson, told the New York Times that they were not suspects in the pipe bomb plot. He said investigators talked to everybody who knew the recipient of the failed bomb and that the couple was told they were cleared.

Sylvia Fluckiger, a lab technician who worked with Bishop at the time, said Bishop had been in a dispute with Rosenberg shortly before the bombs were discovered, though she didn't know the nature of the disagreement.

"It was common knowledge," she told The Associated Press Sunday.

Bishop told Fluckiger she was questioned by police. "They must have had their reasons," Fluckiger said.

Killed in Friday's shooting were Gopi K. Podila, the chairman of the Department of Biological Sciences, and professors Adriel Johnson and Maria Ragland Davis. Of the three people who were wounded, two were in critical condition early Sunday and the third was released from the hospital.

Two stepdaughters of one of the professors killed said they were shocked that Bishop was hired by the university, given her past.

"I think they need to do a little more investigation when coming down to hiring teachers and things like that," said Melissa Davis, whose stepmother was Maria Ragland Davis, on ABC television Monday.

Her sister, Latashia Davis, said she was angry: "How did she even get a job working at the school if she had this type of background?"

Still, those who knew Bishop said nothing suggested she might become violent. Several family members, friends and students said the intelligent and at times awkward teacher seemed normal in the hours before police say she opened fire in a faculty meeting Friday afternoon.

Investigators have declined to discuss a motive, but Bishop didn't hide her displeasure over the fact she'd been denied tenure — a type of job-for-life security afforded to academics.

Police say the gun she's accused of using in the Alabama shooting wasn't registered, and investigators don't know how or where she got it.

Bishop was arrested soon after the shooting and charged with capital murder. Three counts of attempted murder were filed against Bishop over the weekend, according to jail records. Her husband was detained and questioned by police but has not been charged.

James Anderson said his wife had an attorney but would not say who it was. He declined further comment to The Associated Press on Sunday. However, he told the Chronicle of Higher Education earlier in the day that he had no idea his wife had a gun — nor did he know of any threats or plans to carry out the shooting when he dropped her off at the faculty meeting Friday.

Just after the shooting, Anderson told the Chronicle, she called and asked him to pick her up. She never mentioned the shooting, he said.

Bishop was calm as she got into a police car Friday, denying that the shootings occurred. "It didn't happen. There's no way. ... They are still alive."