Binghamton, N.Y., authorities called the gunman who shot 13 people dead at an immigration center a "coward" who planned to fight police but later changed his mind and committed suicide.
Police Chief Joseph Zikuski identified the shooter as 41-year-old Jiverly Wong and said he had voluntarily changed his last name to Voong.
"He arrived wearing body armor," the chief told a news conference Saturday. "At one point in his thinking process, he was going to take on police or at least stop them from stopping him. He must have been a coward. We speculate that when he heard the sirens, he decided to take his own life."
Zikuski said Wong was depressed about his poor English-speaking skills, which he believed he was being teased about, and his recent unemployment.
People "degraded and disrespected" the gunman over his inability to speak English well, Zikuski said on NBC's "Today" show.
"He was terminated from his job at a place called Shop-Vac, and he was very upset about that also," Zikuski told reporters at the press conference.
Click here for photos.
Wong could not find work and complained that his unemployment benefit checks were only $200 a week, said Hue Huynh, a Binghamton grocery store proprietor whose husband worked with him years ago.
Wong had driven a truck in California before recently returning to Binghamton, only to lose a job there, Huynh said.
"He's upset he don't have a job here. He come back and want to work," she said. Her husband tried to cheer him by telling him he was still young and there was plenty of time to find work, but he complained about his "bad luck," she said.
Wong was unmarried and lived with his mother, father and sister, the chief said. He had been taking classes until last month at the center where he committed the massacre, called the American Civic Association.
Zikuski said detectives have spoken to the family, but declined to offer many details "other than to say that some of the behavior he exhibited didn't come as a total shock."
A friend told The Associated Press that Wong was ethnically Chinese but from Vietnam.
Wong had a permit for the two handguns he used, Zikuski said. Most of the victims had multiple gunshot wounds, he said.
Investigators said they had yet to establish a motive for the shooting. It was at least the sixth fatal mass shooting in the U.S. in the past month, and the nation's deadliest since April 2007, when 32 people and a gunman died at Virginia Tech.
"Even if we do know why, the vast majority of us aren't going to understand what would make someone do something as horrible as this," Zikuski told FOX News on Saturday.
Zikuski acknowledged reports that a terrorist group was taking responsibility for the rampage and said that was false.
"As far as we know, there is absolutely no tie to terrorism," he said.
Earlier, other details emerged about Wong's apparent anger and depression.
Friends told the New York Daily News that he was a rage-filled loner who hated America and had an affinity for guns.
He had a strong contempt for the United States and dreams of assassinating the president, said former Shop-Vac co-worker Kevin Greene.
"I asked him if he liked the Yanks," Green told the newspaper, explaining the question was prompted by a New York Yankees T-shirt Wong was wearing. "He said, No I don't like that team. I don't like America. America sucks."
Greene said he lives outside Binghamton, N.Y., where Wong opened fire Friday morning on workers and immigrants taking citizenship courses at a community center. He worked with Wong at the Shop-Vac assembly plant in town until it shut down in November, the News reported.
He used to joke with co-workers about Wong's fury, the paper said, and he told FBI investigators there was banter about how their angry fellow employee might "come in mad one day and shoot people. He seemed like that kind of a guy."
Another former Shop-Vac worker, Donald Ackley, said Wong was often by himself but would make bizarre comments "like he wanted to kill the president." It wasn't clear whether he was referring to President Bush or President Obama.
On Friday, Wong barricaded the back door of the American Civic Association with his car and then opened fire on a room full of immigrants taking a citizenship class.
The killer carried identification bearing the name Jiverly Voong.
On Friday, Wong — wearing a green nylon jacket and dark-rimmed glasses — barricaded the American Civic Association community center's back door with his car, walked in the front and started shooting with two handguns.
Within minutes, 13 people, including a receptionist and immigrants taking a citizenship class, as well as the gunman were dead.
Another receptionist, 61-year-old Shirley DeLucia, played dead after she was shot in the abdomen and called the emergency dispatcher to get police to the scene within two minutes.
Zikuski said the injured receptionist stayed on the phone for 39 minutes, "feeding us information constantly," despite a serious wound in the abdomen.
"She's a hero in her own right," he said.
DeLucia was in critical condition at a hospital Saturday, along with another victim in the same condition and a third in serious condition. A fourth victim was in stable condition at another hospital.
Thirty-seven 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.
Wong 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 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 sister told the AP on Friday that her brother worked at a company where "they make the vacuums."
Initial reports suggested Voong had recently been let go from IBM, which has roots in the region, but a person at IBM said there was no record of a Jiverly Voong ever working there. His father, Henry Voong, does work there as a contractor.
Huynh said her husband had worked with Voong years ago at IBM and that he had recently been let go from IBM again after returning from California.
The attack at the American Civic Association, which helps immigrants settle in this country, came just after 10 a.m. as people from all over the globe — Latin America, China, Kazakhstan, Vietnam, Africa — gathered for English and citizenship lessons in an effort to become a bigger part of their new home.
Wong 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.
Abdelhak Ettouri, a Moroccan immigrant who lives in nearby Johnson City, told the Binghamton Press & Sun-Bulletin he found the back door locked when he tried to flee, then ran to hide in the basement as he heard 12 to 14 shots: "Tak-tak-tak-tak."
Hoi Nguyen of Binghamton said his 36-year-old daughter Phuong Nguyen, who survived the massacre, was taking an English class in the basement when the gunfire started.
"She said it sounded like a firecracker and everyone in the class was startled," he said. "Then the teacher locked the door, called the police, then told everyone they couldn't leave the room."
Police arrived in minutes, heard no gunfire and waited for about an hour before entering the building to make sure it was safe for officers. They then spent two hours searching the building. They led a number of men out in plastic handcuffs while trying to sort out victims from the killer or killers.
The Binghamton region 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 47 people dead in all.
A gunman killed 10 people and himself in Samson, Alabama; shootings that began with a traffic stop in Oakland, California, left four police officers and the gunman dead; an apparent murder-suicide in Santa Clara, California, left six dead; and a gunman went on a rampage at a nursing home last Sunday, killing seven elderly residents and a nurse who cared for them.
On Saturday, a man opened fire on officers during a domestic disturbance call in Pittsburgh, killing three of them, a police official said.
FOXNews.com's Catherine Donaldson-Evans and The Associated Press contributed to this report.