Whatever Byran Uyesugi's motivation for shooting seven colleagues dead at the Xerox company on the outskirts of Honolulu, he has become the latest mass-murderer to stalk the American workplace.
To compound the sense of shock, it happened in Hawaii - a place where, according to local wisdom, things like that simply do not happen. "This shows violence can permeate even paradise," said Jeremy Harris, Mayor of Honolulu.
Uyesugi gave himself up on Tuesday afternoon after a five-hour stand- off with police at the Hawaii Nature Center on a hill above the capital. Having sat in the company van in which he made his getaway, surrounded by police Swat teams pleading with him through bullhorns, the 40-year- old got out, hands in the air, walked to the back of the vehicle and allowed himself to be handcuffed.
Yesterday the public prosecutor was drawing up charges of first-degree murder.
As details emerge, colleagues and witnesses have remarked on the gunman's calm. On his way into the Xerox building, just after 8am, Uyesugi stopped to wish a co-worker good morning and good luck.
Entering a second-floor office, he shot a colleague in the back of the head while he was hunched over a computer terminal. A second colleague put up a struggle before being shot dead.
A third man thought he was witnessing a Halloween prank until he too was fired at. This time the bullet from Uyesugi's 9mm pistol missed.
When someone in the conference room walked out to make a phone call, leaving the door open, Uyesugi sneaked in and shot five people dead at close range. Four were Xerox colleagues, the fifth a visiting executive from IBM. All seven victims were men, ranging in age from 33 to 58, and several had young children.
The gunman appears to have said little or nothing and was "very calm and collected" as he left the building, according to a Xerox employee, Edith Nakamara. He waved goodbye to an acquaintance before hopping into a van and driving off.
A similar calm characterised his life at home on Easy Street, in the Nuuanu neighbourhood, where he had lived all his life with his father and brother. Aside from his goldfish and koi, which he kept in tanks in the back garden, he made furniture and was always doing household tasks, according to neighbours.
His past offered a few clues - 17 firearms registered in his name, a stint on his high school rifle team, a drink-driving conviction and an anger-management course mandated after he kicked in some lift doors at work a few years ago.
An employee at the State Capitol building, where he repaired photocopiers, said he had been showing signs of stress but did not want to talk about it. Co-workers suggested he might have been about to be dismissed from his post, but nobody could confirm this.
Hiroyuki Uyesugi, the gunman's father, said: "We just don't talk about those things. We don't talk about work." Mr Uyesugi also said he wished his son had shot himself.
With workplace shooting rampages becoming increasingly common in the United States - there have been at least four such mass-murders in the past year - sociologists and management experts have tried to come to grips with the causes that move employees to crack.
There were 700 workplace homicides in the US in last year,making murder the second-biggest cause of work-related deaths after car accidents. Most of these, however, are the result of robberies and assaults committed by outsiders; a little over 60 were the result of "office rage".
"What happened in Hawaii is tragic, but it is also atypical," said Kristin Accipter of the Society for Human Resource Management, which conducted one of the recent surveys.
In Hawaii, where the murder rate is markedly lower than in continental USA - there were 17 murders last year in Honolulu, a city of one million - the soul-searching went deeper than the statistics.
The killer of Matthew Shepard, the 21-year-old gay man who was attacked and left tied to a fence, was convicted of murder yesterday.
Aaron McKinney's sentence is due to be announced today and could face execution, despite the death penalty being rarely passed in his state of Wyoming.
McKinney, 22, and his companion Russell Henderson, who has already pleaded guilty and is serving two consecutive life sentences, lured Shepard outside a bar in Laramie, pistol-whipped him and left him to die.