A Vietnamese immigrant who killed 13 people and himself at an upstate New York civic center fired 98 shots from two handguns in just over a minute, according to police.

Ballistics reports show that 41-year-old Jiverly Wong fired 87 times from a 9mm Beretta and 11 times from a .45-caliber handgun.

Click here for photos.

Click here for a list of the victims.

Nearly all of the 13 victims died instantly, police said.

Four others were wounded but survived.

Wong killed himself as police were rushing to the scene. Detectives believe he initially planned to fight them, since he was wearing body armor, but panicked when he heard their sirens and took his life instead.

The gunman's body was found with a satchel containing several full ammunition clips.

Police have speculated that Wong, who was ethnically Chinese but was from Vietnam, was angry over losing a job and frustrated about his poor English-language skills.

Also this week, authorities released the 911 tapes made as the massacre was happening.

"Shots are coming from the second floor ... assailant still in the building ... standby until you get backup," one dispatcher advises police at the scene.

"Nobody go in that building alone," warns another.

Police were told to have those inside "lock the doors" if they were able to communicate with them, but a dispatcher follows up with the information that the doors had no locks on them, so she was instructing those caught in the rampage to use something to barricade them instead.

Almost immediately, the tapes show, it was apparent there were casualties.

One woman, a receptionist whom Binghamton police have labeled a "hero," called 911 after having been shot by Wong.

Click here to hear the 911 calls in a report from MyFOXNY.com.

The Associated Press contributed to this report.