April 8 (Bloomberg) -- The gunman who killed 13 people in a Binghamton, New York, immigrant aid center last week fired 99 shots from two pistols, including a Beretta equipped with high- capacity magazines, police said.

Investigators are still working to unravel why Jiverly Wong, 41, an unemployed immigrant from Vietnam, targeted the upstate city’s American Civic Association, where he had been learning English.

“Ninety-eight casings were recovered at the scene,” Sergeant Arnold Nanni of the Binghamton Police Department said in an interview today. “One casing was found in the folds of a victim’s clothing.”

In a rambling letter received by a local television station, News 10 Now in Syracuse, Wong blamed police for the shooting, saying they had harassed him over nearly two decades both in his home town of Johnson City, outside Binghamton, and in California, where he lived in the early 1990s.

The victims in Binghamton, a city of 45,000 about 170 miles (274 kilometers) northwest of New York City, came from around the world. Two were from the U.S., four from China, two -- a husband and wife -- were from Haiti, and one each came from Vietnam, Iraq, Brazil, the Philippines and Pakistan, the New York Times reported. Four people were wounded.

More than 40 people have died in mass shootings nationwide in the past month. The Binghamton shooting was the nation’s deadliest mass murder since April 2007, when a student killed 32 people at Virginia Polytechnic Institute and State University before turning the gun on himself.

30 Rounds

Nanni said police at the scene had found at least two high- capacity magazines for the Beretta, each capable of holding 30 rounds. Binghamton Police Chief Joseph Zikuski told the Associated Press the other gun used by Wong was a 45-caliber automatic, a larger and heavier gun, with which he fired 11 rounds during the assault.

Nanni said investigators are still trying to establish a timeline for the shooting.

“We have no idea how long it took,” Nanni said. Wong turned one of the guns on himself after shooting the victims inside the building. “We got there in less than a minute when the call came in to us and there were no more shots. We’re still in the process of talking to surviving victims.”

Wong had a New York state pistol permit, first obtained in 1997, with the two handguns used in the shooting registered to it, AP reported.

Lost Job

Zikuski has said that Wong may have been frustrated by his poor command of English and that he had lost a job with a vacuum cleaner company several months ago.

Wong wrote in the letter that when he lived in California, police used remote means to “switch the channel,” “adjust the fan,” and “for connect the music into my ear.”

In the letter, handwritten in capital letters across two sheets of paper and postmarked April 3, the day of the shootings, Wong blamed police for his condition.

“Cop made me lost my job… cop put me become poor,” he wrote.

Wong accused police of trying to force him into automobile accidents 32 times.

He said that in order to judge the undercover policemen who were harassing him, he would have to take at least two people with him “to return to the dust of earth.”

The letter ended with the words: “Cop bring about this shooting. Cop must responsible. And you have a nice day.”

To contact the reporter on this story: Peter S. Green in New York at psgreen@bloomberg.net.

Last Updated: April 8, 2009 11:54 EDT