BINGHAMTON, N.Y. (AP) — The two receptionists at the American Civic Association community center barely had time to react when a gunman stormed in the front door and shot them at close range before firing on a roomful of immigrants taking a citizenship class.

One receptionist survived, playing dead, before crawling under a desk and calling 911.

Police Chief Joseph Zikuski said she stayed on the phone for 90 minutes, "feeding us information constantly," despite a serious wound in the abdomen.

"She's a hero in her own right," he said.

The gunman killed 13 people — a dozen in the classroom — before apparently killing himself.

Four people were critically wounded in the Friday massacre, and 37 others made it out, including 26 who hid for hours in a basement boiler room while police tried to determine whether the gunman was still alive and whether he was holding any hostages, Zikuski said.

Investigators said they had yet to establish a motive for the shooting, which was at least the fifth deadly mass shooting in the U.S. in the past month.

The suspected killer — believed to be a Vietnamese immigrant — 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 man believed to have carried out the attack was found dead in an office with a self-inflicted gunshot wound, a satchel containing ammunition slung around his neck, authorities said. Police found two handguns — a 9 mm and a .45-caliber — and a hunting knife.

A second law enforcement official, also speaking on condition of anonymity, said the handguns were registered to Jiverly Wong, another name the man used. Both officials were not authorized to speak publicly.

Initial reports suggested Voong had recently been let go from IBM. But a person at IBM said there was no record of a Jiverly Voong ever working there.

The attack at the American Civic Association, which helps immigrants settle in this country, came just after 10 a.m.

The gunman parked his car against the back door before barging through the front and opening fire, apparently without saying a word. He then entered a room just off the reception area and fired on a citizenship class while terrified people scrambled into a boiler room and a storage room.

The center was filled with people from countries as far off as Kazakhstan and Uzbekistan, all working to become more a part of their new home — learning English, taking a class to gain U.S. citizenship. The gunman may have walked a similar path to become an American decades ago.

"I heard the shots, every shot. I heard no screams, just silence, shooting," said Zhanar Tokhtabayeva, a 30-year-old from Kazakhstan who was in an English class when her teacher screamed for everyone to go to the storage room. "I heard shooting, very long time, and I was thinking, when will this stop? I was thinking that my life was finished."