by John Bentley, Paul Bogosian and Phil Hirschkorn
(CBS News) HARRISBURG, Pa. - The gun used to murder Mary Moola never should have been sold to her killer, Emmanuel Nzambi.
Despite having spent four years in a Pennsylvania mental hospital, in 2005, Nzambi, who battled schizophrenia for 20 years, was able to buy a 9mm Ruger pistol from Bass Pro Shops.
Two years later, in May 2007, he walked into the doctor's office where Moola worked, fatally shot her in the chest, and fled. It was her husband's office, and he had been Nzambi's psychiatrist.
The Moola murder remained unsolved until two months later, when Nzambi shot and wounded a neighbor. Ballistics showed the same gun was used in both crimes.
"Any person who has been involuntarily committed should not have the ability to purchase a handgun -- period," said Brian Perry, Nzambi's defense attorney. "This is a person who was severely mentally disabled."
Nzambi will spend the rest of his life incarcerated, but Perry believes the shootings could have been prevented if Pennsylvania at the time had reported names of its mentally ill residents to the national database of people banned from buying guns.
"He's a perfect example of someone who slipped through the cracks," Perry said.
Since 1998, when the FBI launched the National Instant Criminal Background Check System, known as NICS, the database has grown to include the names of more than 8.3 million people prohibited from purchasing guns.
The database includes illegal immigrants, felons, fugitives, spouse abusers, drug addicts, and the mentally ill.
Under federal law, anyone who has been committed to a mental institution or deemed mentally unstable by a judge are prohibited for life from purchasing a gun.
For the past 15 years, Pennsylvania did collect the names of its seriously mentally ill residents, but until this month, it never sent that information to NICS.
Through 2011, Pennsylvania was the most populous of 23 states that had submitted fewer than 100 disqualifying mental health records to NICS, and it was among the 17 states to submit fewer than 10 such records, according to the report, "Fatal Gaps," by Mayors Against Illegal Guns. (MAIG).
When MAIG updated its data this month, it found that two states previously inactive, Delaware and Idaho, had begun submitting mental health records.
By submitting 18,699 records last year, MAIG reported, Delaware has become the second most compliant state on a per capita basis behind Virginia, which sprang into action only after the 2007 Virginia Tech University massacre.
In December 2005, just 16 months before his killing spree at Virginia Tech, gunman Seung-Hui Cho underwent a psychiatric evaluation. A judge deemed Cho a danger to himself and ordered him to get treatment, which never did.
Virginia had not sent Cho's name to NICS, so when he went to purchase a Glock 9mm and a Walther P22, both semi-automatic pistols, he twice passed a background check. On April 16, 2007, Cho shot 49 people - killing 32 and wounding 17 -- before shooting himself.
"This is not one person's problem, this is every county's problem, every state's problem, and it's a national problem," said Pennsylvania's new attorney general, Kathleen Kane, who took office this week after winning election in part on a gun control platform.
In the past two weeks, CBS News has learned, the Pennsylvania State Police sent 642,000 names collected between 1998 and 2012 of residents once diagnosed with mental illness or committed to a mental hospital to NICS.
"It protects Pennsylvanians, and it also protects people from other states, because now a Pennsylvania resident can no longer go into another state and obtain a weapon that they would not legally be able to obtain in Pennsylvania," Kane said.
In correspondence reviewed by CBS News, Pennsylvania State Police informed the FBI last December 19, just five days after the mass shooting in Newtown, Connecticut, that it would begin transmitting mental health records.
A spokeswoman said the police had decided to share records prior to the events in Newtown. Earlier, Pennsylvania State Police had sought guidance from the FBI and the Bureau of Alcohol Tobacco and Firearms (ATF) about whom of the involuntarily committed were ineligible to buy guns under federal law.
Kane said states still need clearer guidelines on who should be on the prohibited list.
"We all have different definitions of mental illness. We all have different definitions of in-patient treatment or institutionalization, and we need to get those all on the same track," she said.
The FBI told CBS News eight states have submitted only five or fewer names prohibited for mental health reasons, but declined to identify those states, and suggested submitting a Freedom of Information Act request.
CBS News' phone calls to state law enforcement and health officials in the two dozen states identified in the 2011 MAIG report as the least compliant reporters of mental health records found these eight states are currently not reporting names - Alaska, Hawaii, Massachusetts, Montana, Oklahoma, South Dakota, and Vermont.
This week, U.S. Senator Tom Coburn of Oklahoma said President Obama is "right to take steps to strengthen mental health databases and reporting to the NICS system, so we can ensure that guns do not end up in the hands of criminals or those who are a threat to themselves or others."
On Friday in Massachusetts, state senator David Linsky introduced legislation to clear government and health officials to report names.
"These are people who have been committed by a judge into a state mental health facility, because they are a danger to themselves or to other people in the community," Linsky said. "These aren't people who have minor problems and who want to see a therapist because of a divorce or a problem in their family."
To date, neither the Massachusetts State Mental Health Department nor private hospitals in the state have been willing to share names of the mentally ill.
"This is a place where public safety trumps any possible privacy right," Linsky said. "If you don't want to have somebody to get access to the fact that you were committed to a mental hospital, then don't buy a gun, don't apply for a gun license."
The pro-gun rights National Rifle Association told CBS News that it was deeply involved in the development of NICS and has strongly supported state implementing legislation.
By the end of last year, there were more than 1.8 million people banned from buying guns for mental health reasons, according to the FBI.
The improved reporting in Pennsylvania and other states is too late to have stopped Emmanuel Nzambi from his two shootings.
"If he did not have an access to a gun this would not have happened," his defense attorney, Brian Perry, said. "His mental illness pulled this trigger."
Abigail Collins and Linda Nguyen contributed to this story.