A former biology professor accused of pulling a gun from her purse and opening fire at a faculty meeting pleaded guilty Tuesday to killing three colleagues and wounding three others at the University of Alabama in Huntsville in 2010. Amy Bishop, 47, pleaded guilty to one count of capital murder involving two or more people and three counts of attempted murder during a hearing in Huntsville. She had earlier pleaded not guilty, and her lawyers said she planned to use an insanity defense. Prosecutors agreed to recommend a sentence of life without parole for the capital charge, and three life sentences for the attempted murder charges. Sentencing will follow a brief trial on Sept. 24 before Madison County Circuit Judge Alan Mann. Prosecutors say Bishop opened fire at the meeting on Feb. 12, 2010. Her attorneys say Bishop had mental problems; she signed a plea agreement with a barely legible scrawl. Bishop, who lived with her family in Huntsville before the shootings, also is charged with killing her brother in Massachusetts in 1986. The shooting of 18-year-old Seth Bishop had been ruled an accident after Amy Bishop told police she shot him in the family's Braintree home as she was trying to unload her father's gun. But the Alabama slayings led to a new investigation and charges. In the school shooting, police and people who knew Bishop have described the Harvard University-educated researcher as being angry over UAH's refusal to grant her tenure, a decision that effectively would have ended her employment in the biology department. The gunfire killed Bishop's boss, biology department chairman Gopi Padila, plus professors Maria Ragland Davis and Adriel Johnson. Professors Joseph Leahy, staff aide Stephanie Monticciolo and assistant professor Luis Cruz-Vera were shot and wounded. Debra Moriarity was in the faculty meeting at the time of the shooting and is now biology chairman at the school. Prosecutors who met with potential witnesses last Friday said there was a possibility of a plea agreement before the trial began on Sept. 24, she said. "So I'm not totally surprised by it, but I am surprised it happened this soon," she said. After Bishop was indicted, prosecutors said Braintree police in 1986 failed to share important evidence, including the fact that Bishop, after she shot her brother in the chest, tried to commandeer a getaway car at gunpoint at a local car dealership, then refused to drop her gun until police officers ordered her to do so repeatedly. Those events were described in Braintree police reports but not in a report written by a state police detective assigned to the district attorney's office. Larry Tipton, Bishop's lawyer in the Massachusetts case, said it will be up to Norfolk District Attorney Michael Morrissey to decide whether to put Bishop on trial for murder in her brother's killing, now that she has pleaded guilty in Alabama. David Traub, a spokesman for Morrissey, said prosecutors will wait until after the Sept. 24 sentencing to decide what to do in the Massachusetts case. Moriarity said she was OK with the death penalty being off the table and was relieved that victims wouldn't have to sit through a trial to see whether jurors convict Bishop. "I'm glad it's a recognition of the crimes she committed and not trying to get out of something through claiming a mental defect," she said. Personally, Moriarity said she was relieved that the case is nearly over. "I had a horrible dream about the trial last night," said Moriarity. Bishop pointed the gun at her and pulled the trigger but it failed to fire. Moriarity said Leahy, who was shot in the head, returned to teaching a full load of classes and conducting research this fall at the school. The only lingering effects he suffers are reduced eyesight, she said. "Mentally he is on top of things," she said. "It's an absolute miracle. He's a miracle." Copyright 2012 The Associated Press.