BOSTON – The husband of the Alabama professor accused of fatally shooting three colleagues once said he wanted violent revenge on a doctor who gave his wife a bad job review, according to documents that feed growing evidence the woman showed signs of violence long before the latest episode.

Amy Bishop is charged with killing three colleagues at the University of Alabama-Huntsville on Feb. 12. Investigative files released Tuesday to The Associated Press by the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives show that Bishop and her husband, James Anderson, were questioned in 1993 in the attempted mail bombing of Dr. Paul Rosenberg of Boston’s Children’s Hospital.

Rosenberg told investigators he played a role in Bishop’s resignation as a postdoctorate research fellow in the hospital’s neurobiology lab. A pipe bomb package was sent to his home weeks later.

The ATF report states that on April 27, 1995, authorities re-interviewed a witness who admitted that during a conversation in 1993, ”Anderson stated that he wanted to get back at victim Dr. Rosenberg and that he wanted to shoot him, bomb him, stab him or strangle Rosenberg.”

The couple were never charged, and the case remains unsolved. A phone message left with Anderson was not immediately returned. Roy W. Miller, an attorney for Bishop, declined to comment through an assistant on the contents of the ATF documents, which were first reported by The Boston Globe.

But Anderson previously told the AP he and his wife were among a number of innocent people questioned by investigators.

The Harvard-educated Bishop, 45, remains jailed in Huntsville, charged with capital murder and attempted murder in the Alabama shooting, which also wounded three other colleagues. Police have not offered a motive, but colleagues say she had complained for months about being denied the job protections of tenure.

Her attorney has said she needs mental evaluations and is laying the groundwork for an insanity defense.

Since the Alabama shooting, several disturbing episodes in Bishop’s past have come to light.

In 1986, at age 21, she fatally shot her 18-year-old brother in what was ruled an accident and produced no criminal charges. In 2002, she was accused of punching a mother in an argument over a booster seat in a Massachusetts restaurant; the charges were dismissed and the judge refused to order her into an anger management program.

And, in 1993, Bishop and her husband were suspects in the mail bomb.

The ATF files say two suspects — a married couple — were identified during its investigation with the U.S. Postal Inspection Service. One of the suspects ”had quit employment” and was ”on the verge of a nervous breakdown,” according to witnesses.

The name of the witness is blacked out, and it is unclear from the records whether investigators found the witness credible. The names of Bishop and Anderson are also blacked out in most places, but a law enforcement official familiar with the case confirmed they were the suspects. The official was not authorized to speak publicly and spoke on condition of anonymity.

The report says the wife ”had been having employment related problems” with Rosenberg and around the time of the mailing had quit her job with Rosenberg.

Rosenberg also told investigators that he and others felt Bishop had problems with depression. ”He stated that she was not stable,” the ATF report says.

The doctor told investigators that over the years there had been ”growing concern” among colleagues about the wife, who ”has exhibited violent behavior.”

Rosenberg told authorities he and his wife returned to their Newton home after a weeklong vacation and found a package. When he saw wires, he immediately fled the house with his wife and called police. The package contained 9-volt batteries, two pipe bombs with black powder and two roller lever switches. The bombs did not go off.

The ATF report indicates that black powder used in the bombs and other evidence led them to search the home and office of Bishop and Anderson but that analyses were ”unable to tie any of the items in the searches with the suspect explosive device.”