By Verna Gates

BIRMINGHAM, Alabama (Reuters) - A former biology professor at the University of Alabama at Huntsville avoided the death penalty by pleading guilty on Tuesday to murder and attempted murder charges for fatally shooting three co-workers on campus in 2010, court officials said.

Amy Bishop, 47, last year had pleaded not guilty by reason of mental disease or defect. She was accused of shooting dead three colleagues and wounding three others during a biology department staff meeting in February 2010.

Colleagues believed the Harvard-trained biologist and mother of four, who also has been charged in Massachusetts with the 1986 shooting death of her teenage brother, was angry that the school had denied her tenure.

Bishop now will face up to life in prison in exchange for her guilty plea on one count of capital murder, which in Alabama can cover the deaths of two or more people, and three counts of attempted murder, according to the district attorney's office.

A hearing is now scheduled for September 24, the day her murder trial had been due to begin. A jury must decide the punishment for a capital murder charge in Alabama, and attorneys in the case will likely ask jurors to confirm that life in prison without parole is the appropriate sentence, according to Richard Jaffe, a defense attorney not connected to the case.

Details on what prompted the plea agreement were unclear on Tuesday, with the defense and prosecutors instructed by the judge not to discuss the case.

After Bishop's arrest in the university shooting, authorities in Braintree, Massachusetts, charged her in the 1986 death of her brother. That death initially was ruled accidental, based on the testimony of the family.

Massachusetts authorities said they would decide whether to continue pursuing their case against Bishop based on what happens in Alabama.

"We will be looking to see what the outcome is before deciding on how to proceed with the homicide of her brother Seth," said David Traub, spokesman for the Norfolk County district attorney.

(Reporting by Verna Gates; Writing by Colleen Jenkins; Editing by Cynthia Johnston and Will Dunham)