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The All-Tech Investment Group - in whose offices four people were shot - said it was "shocked and saddened by the senseless tragedy".

Police remove the body of one of Barton's children

"It is difficult to understand this kind of horrific event," a company statement said. "No explanation can alleviate our grief or bring a sense of closure to the horror of these shootings."

Another spokeswoman for the company said she "did not know what precipitated this rampage".

"We understand that he had marital difficulties and that he was going through a divorce," she added.

The Atlanta Police Department is examining four notes - three of them hand-written, the fourth typed on a computer - found with the bodies of Barton's second wife and two children at their home in Stockbridge, 16 miles south-east of Atlanta.

Police believe he beat them to death at least two days prior to the shootings.

They are also examining reports that Barton may have lost more than $70,000 while speculating on the stock exchange.

Traumatic afternoon

The drama began shortly before 3pm local time (1900GMT) on Thursday, when Mr Barton walked into the All-Tech offices on Piedmont Road in Atlanta's Buckhead financial district.

Witnesses say he appeared calm and spoke to staff about the state of the financial markets, which had seen massive falls that day over worries about US inflation.

Moments later he produced a pair of handguns - later identified by police as a 9mm and a .45-calibre - and opened fire, killing four office workers.

One witness quoted the killer as saying, shortly before he began shooting: "I hope this doesn't ruin your trading day."

Office staff were evacuated by police

He then moved across the road and began shooting at another office building in the Piedmont Centre where another five people were killed.

At least a dozen people injured in the shootings were still in hospital on Friday.

Three of the wounded at Atlanta's Grady Hospital were in critical condition, according to a hospital spokeswoman, though they were said to be able to speak to nursing staff.

Police chronology

This is the full sequence of events, as outlined by the Atlanta Police Department:

• 1445 Barton enters All-Tech Investment Services in the Securities Centre, kills four
• 1450 He crosses 6-lane Piedmont Road, enters Momentum Securities brokerage in Piedmont Centre, kills five
• 1500 Police arrive on scene after receiving 911 emergency call
• 1523 Police in Henry County find bodies of Barton's second wife and two children
• 1558 First of three ambulances arrives; office workers evacuated by police
• 1715 Mayor Campbell holds news conference to announce fatalities
• 2000 Barton shoots himself after being stopped by police

'Our nation is in pain'

President Clinton expressed his sadness over the shootings, and said federal officials were assisting state and local authorities in their investigation.

"Our thoughts are primarily with the families of the victims and those who are struggling for their lives in the hospital," said Mr Clinton, who is in Sarajevo for a Balkan summit.

"We have no information at all" on what set off the killing spree, Atlanta Mayor Bill Campbell said late Thursday, "except we're certain Mr. Barton came to Piedmont Road and killed nine people."

The Mayor of Atlanta, Bill Campbell, called for prayers "for our nation and for our city; these are unspeakable tragedies".

"I think our nation is in pain," he said; "there is a cancer that's eating at the heart of this country."

Previous suspicions

Mr Barton was the main suspect in the unsolved double murder of his 36-year-old first wife, Debra, and his mother-in-law, Elois Spivey, on Labour Day in 1993.

The two women were found beaten to death in a camper van in east Alabama.

The BBC's Brian Barron from Atlanta "Barton was mentally unbalanced and in a vengeful mood"

Mr Barton - who is reported to have taken out an insurance policy worth $600,000 on his first wife's life - was subsequently awarded custody of the couple's two children.

His former father-in-law told a local newspaper, the Atlanta Journal-Constitution, that the latest killings "completed what Barton had started six years ago".

"The man has destroyed nearly my whole family," said Bill Spivey. "The man who it appears killed my wife and daughter also killed my two grandchildren."

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