NY shooter's note: 'Have a nice day' - April 8, 2009

The gunman who killed 13 people and himself in a New York state immigrant centre last Friday had sent a letter to a television station before his shooting spree that ended with the words "And you have a nice day".

Jiverly Wong, a 41-year-old Vietnamese immigrant, wore body armour into the Binghamton building where he had been studying English and opened fire on immigrants taking an exam to become US citizens.

"I am Jiverly Wong shooting the people," began the letter that was received by News 10 Now of Syracuse, New York, on Monday. It was mailed on Friday but dated March 18, more than two weeks before the attack.

Binghamton Police Chief Joseph Zikuski yesterday said the letter, which was mailed in a package including Mr Wong's driver's licence and gun permit, was believed to be authentic.

Mr Wong included photos of himself with two handguns - possibly the two he used in the attack in Binghamton, a city of 45,000 people about 240 kilometres northwest of New York City.

Mr Wong apologised for his poor English in the rambling, hand-written letter of two pages.

"Of course you need to know why I shooting?" he wrote, but never fully explained the reason. He made some unclear references to police harassment in New York and California before ending with the salutation: "And you have a nice day".

Mr Zikuski said on Saturday no motive had been determined but he confirmed reports that Mr Wong had felt degraded by his inability to speak English and by a recent job loss.

The letter has been sent to an FBI behavioural analysis unit, Mr Zikuski said.

"There's obviously some mental health issues there, we saw some religious overtones," he said.

Authorities were also trying to recover information from a computer, Mr Zikuski said.