A biology professor charged with shooting dead three people at an American university fatally shot her teenage brother more than two decades ago.
The case was logged as an accident and never came to court, reports the BBC.
Amy Bishop, 42, is now in custody accused of killing three members of staff during a faculty meeting at the University of Alabama at Huntsville.
Police said she used a 9mm weapon armed with 16 bullets, which was later found in the women's bathroom.
At a news conference in Dr Bishop's former home town of Braintree Massachusetts, police chief Paul Frazier revealed that the biology professor killed her brother in 1986 when she was 20-years-old.
At the time it was reported as being an accident, however Chief Frazier said officers who were there told him Dr Bishop shot her brother three times after an argument and fled the scene before being arrested.
She was never charged with the crime and official records of the incident have been missing since 1987.
Local television station WAFF, citing local authorities, says in Huntsville the shooter opened fire after learning at a biology faculty meeting that she would not be granted tenure.
College spokesperson Ray Garner says the three killed were the head of department and two other professors. He says two of those injured in the shooting remain in critical condition while a third is stable.
The incident is the latest in a series of school shootings in the United States - most of them carried out by students. It also comes amid an ongoing debate in the US about gun control.
In April 2007, student Seung-Hui Cho killed 32 people at the Virginia Tech university, before turning his gun on himself.
In 1999, two teenagers went on a rampage at Columbine School, Colorado, gunning down 13 people before killing themselves.
In the first six weeks of this year alone several shootings have already been reported around the country, AFP reports.