That changed when Mr Voong, who was believed to have been recently made redundant by IBM, walked in with a high-powered rifle.
Zhanar Tokhtabayeva, 30, from Kazakhstan, was in an English class when she heard a shot and the teacher shouted at everyone to get into a storeroom.
"I heard the shots, every shot. I heard no screams, just shooting," she said. "I heard shooting, for a very long time and I was thinking, when will this stop? I was thinking that my life was finished."
Alex Galkin, from Uzbekistan, was also in an English lesson. "It was just panic," he said.
"People were there in the process of being tested for their citizenship," said the Republican Congressman Maurice Hinchey, whose district includes Binghamton. "It was in the middle of a test. He just went in and opened fire."
Leslie Shrager, a Binghamton University student living next door to the centre, said: "One of our housemates thought they heard banging of some kind.
"But when you're living in downtown Binghamton, it's always noisy. Literally two minutes later the cops came and got us out."
The American Civic Association's president, Angela Leach, was "very upset" and worried about her secretary, a friend at her home told reporters. "For some reason she had the day off today. She doesn't know anything, she's as shocked as anyone," said Mike Chanecka.
Others were left waiting for news of friends and relatives. Omri Yigal, an immigrant from the Philippines, said his wife Delores had been in an English lesson. "At this point, I know the scale of what happened, but I just hope Delores is okay," he said. "I haven't got any information. The only thing I have right now is hope."
The New York State Governor David Paterson said the shooting was "probably the worst crime and tragedy in the history of this city".
"These were classes for those who wanted to become citizens and become part of the American dream," he said. "When are we going to be able to curb the violence that is so fraught and so rapid that we cannot even keep track of the incidents any more?"