An ex-US Marine who had suffered from depression and once tweeted about killing "everyone I see" opened fire in camouflage gear at a supermarket, gunning down two co-workers before killing himself.
Terence Tyler, 23, left his night clerk shift at a Pathmark store in Old Bridge Township, New Jersey, at around 3.30am, drove off and returned to the closed store 20 minutes later armed with a handgun and an assault rifle similar to an AK-47, Middlesex County Prosecutor Bruce Kaplan said.
About 12 to 14 workers were still there, inputting new prices into the computer, when Tyler fired more than 16 rounds from his rifle - shooting at an employee standing outside and firing as he entered the store, blowing out the front windows.
He shot at five other workers in an aisle, killing Christina LoBrutto, 18, and Bryan Breen, 24, Mr Kaplan said.
"I do not believe that they were specifically targeted. I believe everybody in the store was a target," he said.
Tyler, who began working at the supermarket less than two weeks ago, drew his handgun and killed himself, the prosecutor said.
The motive was under investigation, but family members said Tyler had been discharged from the Marines two years ago after suffering from depression and had never got over his mother's death; the shooting happened around that five-year anniversary, they said.
And on a Twitter account in 2009, with a photograph identified by family members as Tyler, a post talks about hating US Marine life. "I'm starting to see why plp go on killin sprees," he wrote in October 2009, using the handle (at)Tylerbkstyle. And these (obscenity) are reeeeeeally pushin my kill everyone I see button."
At the top of Tyler's Facebook page reads the motto "Be optimistic. All the people you hate are going to eventually die".
Mr Kaplan and police walked through the shooting scene at the supermarket on Friday, with two long windows in the front shot through. Evidence markers were placed next to broken glass outside the store, in a suburban shopping centre about 40 miles south of Manhattan. Several ammunition magazines were recovered along with Tyler's rifle and a .45-calibre handgun.