By WILLIAM KATES, Associated Press Writer William Kates, Associated Press Writer â 2 mins ago BINGHAMTON, N.Y. â A gunman barricaded the back door of a community center with his car and then opened fire on a room full of immigrants taking a citizenship class Friday, killing 13 people before apparently committing suicide, officials said. Investigators said they had yet to establish a motive for the massacre, which was at least the fifth deadly mass shooting in the U.S. in the past month alone. The gunman â believed to be a Vietnamese immigrant himself â had recently been let go from IBM, said Rep. Maurice Hinchey, whose congressional district includes Binghamton. But IBM could not immediately confirm that. The attack came just after 10 a.m. at the American Civic Association, an organization that helps immigrants settle in this country. Police Chief Joseph Zikuski said the gunman parked his car against the back door, "making sure nobody could escape," then stormed through the front, shooting two receptionists, apparently without a word. The killer then entered a room just off the reception area and fired on a citizenship class. "The people were trying to better themselves, trying to become citizens," the police chief said. One receptionist was killed, while the other, who was shot in the abdomen, pretended to be dead, then crawled under a desk and called 911, he said. Police said they arrived within two minutes. The rest of those killed were shot in the classroom. Four people were critically wounded. The man believed to have carried out the attack was found dead with a self-inflicted gunshot wound in an office, a satchel containing ammunition slung around his neck, authorities said. Police found two handguns â a 9 mm and a .45-caliber â as well as a hunting knife, authorities said. Thirty-seven people in all were rescued from the building, included 26 who hid in the boiler room in the basement, cowering there for three hours while police methodically searched the building and tried to determine whether the gunman was still alive and whether he was holding any hostages, Zikuski said. Those in the basement stayed in contact with police by cell phone, switching from one phone to another when their batteries ran out, Zikuski said. Others hid in closets and under desks. At one point, police led a number of men out of the building in plastic handcuffs while they tried to sort out the victims from the killer or killers. Most of the people brought out couldn't speak English, the chief said. Alex Galkin, an immigrant from Uzbekistan, said he was taking English classes when he heard a shot and quickly went to the basement with about 20 other people. "It was just panic," Galkin said. Zhanar Tokhtabayeva, a 30-year-old from Kazakhstan, said she was in an English class when she heard a shot and her teacher screamed for everyone to go to the storage room. "I heard the shots, every shot. I heard no screams, just silence, shooting," she said. "I heard shooting, very long time, and I was thinking, when will this stop? I was thinking that my life was finished." Gov. David Paterson said the massacre was probably "the worst tragedy and senseless crime in the history of this city." Noting mass killings in Alabama and Oakland, Calif., last month, he said: "When are we going to be able to curb the kind of violence that is so fraught and so rapid that we can't even keep track of the incidents?" The community center was holding class "for those who want to become citizens of the United States of America, who wanted to be part of the American Dream, and so tragically may have had that hope thwarted today," the governor said. "But there still is an American dream, and all of us who are Americans will try to heal this very, very deep wound in the city of Binghamton." The suspected gunman carried ID with the name of 42-year-old Jiverly Voong of nearby Johnson City, N.Y., but that was believed to be an alias, said a law enforcement official, speaking on condition of anonymity. The police chief would not confirm the name of the dead man with the ammunition satchel, saying authorities were still trying to establish with certainty that he was the gunman. "We have no idea what the motive is," Zikuski said. He said the suspected gunman "was no stranger" to the community center, and may have gone there to take a class. A woman who answered the phone at a listing for Henry D. Voong said she was Jiverly Voong's sister but would not give her name. She said her brother had been in the country for 28 years and had citizenship. "The police just called me and said he got shot," she said. Asked if she was aware that he might have been involved in the shooting, she said: "How? He didn't have a gun. I think somebody involved, not him. I think he got shot by somebody else." "I think there's a misunderstanding over here because I want to know, too," she said. Waiting outside a Catholic Charities office where counselors were tending to relatives of victims, Omri Yigal said his wife, Delores, was taking English lessons when the gunman attacked. He had no word on what happened to her. "At this point, I know the scale of what happened, but I just hope Delores is OK," the Filipino immigrant said. "I haven't got any information. ... The only thing I have right now is hope." The American Civic Association helps immigrants in the Binghamton area with citizenship, resettlement and family reunification. The shootings took place in a neighborhood of homes and small businesses in downtown Binghamton, a city of about 47,000 situated 140 miles northwest of New York City. The Binghamton area was the home to Endicott-Johnson shoe company and the birthplace of IBM, which between them employed tens of thousands of workers before the shoe company closed a decade ago and IBM downsized in recent years. A string of attacks in the U.S. in the last month left 44 people dead in all. A gunman killed 10 people and himself in Samson, Ala.; a traffic stop shootout in Oakland, Calif., left four police officers and the gunman dead; an apparent murder-suicide in Santa Clara, Calif., left six dead; and a gunman went on a rampage at a nursing home Sunday, killing seven elderly residents and a nurse who cared for them.