At least 13 people died after the assailant went on a shooting spree at the centre where aid is given to immigrants, before he shot himself dead.
Al Jazeera reporter Kristen Saloomey said the gunman is believed to have been a 42-year-old immigrant who had recently lost his job and was distressed after being teased and humiliated over his poor English language skills.
Heavily armed police, backed by commandos and FBI agents, surrounded the American Civic Association building in Binghampton, northern New York, on Friday after the incident was first reported.
The man had entered the building in Binghamton, about 240 km northwest of New York city, and shot two receptionists, Joseph Zikuski, the Binghampton police chief, said.
|Police say the attack was premeditated [Reuters]
"It obviously was premeditated,'' said Zikuski.
He said the gunman had blocked the centre's rear exit with his car.
"He made sure nobody could escape,' he said.
One receptionist was killed, but another pretended to be dead, then crawled to a desk and called authorities, he said.
Zhanar Tokhtabayeva, from Kazakhstan, said she was in an English class when she heard a shot and her teacher screamed for everyone to hide in a storage room.
"I heard the shots, every shot. I heard no screams, just silence, shooting,'' she said.
"I was thinking, when will this stop? I was thinking that my life was finished.''
The American Civic Association helps immigrants in the Binghamton area with citizenship applications, according to US Citizenship and Immigration Services.
Shooting incidents have become increasingly common in the US, where guns are widely available and the rights to own them are fiercely debated.
In 2007, in one of the worst incidents, a student went on a gun rampage, killing 32 people at Virginia Tech University in Blacksburg, Virginia.