Authorities in Binghamton are studying a report from the FBI's Behavioral Analysis Unit on Jiverly Wong. It was a year ago that the Vietnamese-born loner opened fire at the American Civic Association, killing 13 people and wounding four others. YNN's Bill Carey says the report has not been made public, but its findings confirm just how much worse the events of 2009 could have been.

BINGHAMTON, N.Y. -- In the weeks leading up to April 3rd, 2009, Jiverly Wong spent hours on computers at the Binghamton public library. A daily wipe of computer memory has kept authorities from knowing what exactly he was doing, but from the start, profilers have believed he was researching the actions of Seung Hi Cho, the gunman who had killed 34 people the previous year at Virginia Tech.

"The FBI Behavioral Analysis Unit certainly speculated, because it's common in many people who commit these kind of crimes, that he may have been examining other events such as the Virginia tech shooting," said Broome County District Attorney Gerald Mollen.

But there is also a deadly trend among mass killers, a desire to outdo the shootings of the past. The FBI experts believe Wong was prepared to kill far more people and he was certainly carrying enough ammunition to do so. But it was his desire for control, control over how and when he would die, that put an early end to the assault.

"The psychiatrist at the Behavioral Analysis unit at the FBI tells me it's very likely the quick response from the police, hearing the sirens, is what caused him to take his own life. He was probably not finished doing his mission," said Binghamton Police Chief Joseph Zikuski.

After the shooting, when police visited Wong's home, they found a single sheet of paper left or them. On it was written an obscenity and the words "no note." Wong would also control his own story of why he had carried out the attack.

He did so in a rambling, two page letter we received three days later. In it, he spoke of a long battle against persecution by police. The letter confirming the gunman was in the deep grips of paranoia and schizophrenia.

"A guy who's very, very angry and hostile, but also felt as though he had absolutely no control over his life because of his persecution. And so this is his chance, in his own words, to play a judge, 'take a judge's role,' and have that control and be in control for once," said Dr. James Knolls, a forensic psychiatrist.

There had been opportunities to head off the delusional spiral of Jiverly Wong. After reporting hallucinations back in the 1990s, Wong's father had taken him for an examination. There was no apparent follow up. And just a week before the shootings, a final chance for someone to intervene. Wong's sister told police she had scolded him for making a mess in the kitchen. He responded by beating her. The girl never called police, fearful that her brother might kill her.

With his long standing complaints against police, why didn't Jiverly Wong carry out his attack at a police station? The profilers say he knew that at a police station, he would face a gun battle and he wanted an easy target. They have found no reason for the targeting of the Civic Association, except for the fact that it was a building Wong was familiar with and that there would be plenty of potential victims inside.